SECURITIES AND EXCHANGE COMMISSION

                             Washington, D.C. 20549


                                    FORM 11-K


(Mark One)

[X] ANNUAL REPORT  PURSUANT TO SECTION 15(d) OF THE  SECURITIES  EXCHANGE ACT OF
    1934

For the fiscal year ended December 31, 2003

OR

[ ] TRANSITION  REPORT PURSUANT TO SECTION 15(d) OF THE SECURITIES  EXCHANGE ACT
    OF 1934


For the transition period from ____ to ____

Commission file number 333-82306

     A. Full title of the plan and the address of the plan,  if  different  from
that of the issuer named below:

          Employees' Thrift Plan of Indianapolis Power & Light Company

     B. Name of  issuer  of the  securities  held  pursuant  to the plan and the
address of its principal executive office:

                               The AES Corporation
                             1001 North 19th Street
                               Arlington, VA 22209

                              REQUIRED INFORMATION

     A list of the required financial statements filed as part of this Form 11-K
is set forth on page F-1. The consent of Deloitte & Touche to the  incorporation
by reference of these financial  statements into the AES Corporation's  Form S-8
Registration  Statement relating to the Plan (Registration No. 333-82306) is set
forth hereto as Exhibit 23. The certification of the chief executive officer and
the chief financial officer of Indianapolis  Power & Light Company,  pursuant to
18 U.S.C. ss.1350, is attached hereto as Exhibit 99.





EMPLOYEES' THRIFT PLAN OF
INDIANAPOLIS POWER & LIGHT COMPANY

TABLE OF CONTENTS
----------------------------------------------------------------------------------------------------------------------
                                                                                                                  Page

                                                                                                                
REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM                                                            1

FINANCIAL STATEMENTS:

   Statements of Assets Available for Benefits as of December 31, 2003 and 2002                                    2

   Statement of Changes in Assets Available for Benefits for the Year Ended
     December 31, 2003                                                                                             3

   Notes to Financial Statements                                                                                  4-7

SUPPLEMENTAL SCHEDULE:                                                                                             8

   Form 5500, Schedule H, Part IV, Line 4i--Schedule of Assets (Held at End of Year)
     As of December 31, 2003                                                                                       9


NOTE:     Schedules not filed herewith are omitted because of the absence of the
          conditions  under  which they are  required by  Department  of Labor's
          Rules and Regulations for Reporting and Disclosure under the Employees
          Retirement Income Security Act of 1974.





REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM


Employees' Pension Committee of the Employees' Thrift Plan
of Indianapolis Power & Light Company

We have audited the accompanying  statements of assets available for benefits of
the Employees' Thrift Plan of Indianapolis Power & Light Company (the "Plan") as
of December  31, 2003 and 2002,  and the related  statement of changes in assets
available  for benefits for the year ended  December 31, 2003.  These  financial
statements are the responsibility of the Plan's  management.  Our responsibility
is to express an opinion on these financial statements based on our audits.

We conducted  our audits in  accordance  with  standards  of the Public  Company
Accounting Oversight Board (United States). Those standards require that we plan
and perform the audit to obtain reasonable assurance about whether the financial
statements are free of material misstatement.  An audit includes examining, on a
test basis,  evidence  supporting  the amounts and  disclosures in the financial
statements.  An audit also includes assessing the accounting principles used and
significant  estimates  made by  management,  as well as evaluating  the overall
financial  statement  presentation.   We  believe  that  our  audits  provide  a
reasonable basis for our opinion.

In our  opinion,  such  financial  statements  present  fairly,  in all material
respects, the assets available for benefits of the Plan at December 31, 2003 and
2002,  and the  changes  in assets  available  for  benefits  for the year ended
December 31, 2003, in conformity with accounting  principles  generally accepted
in the United States of America.

Our audits  were  conducted  for the  purpose of forming an opinion on the basic
financial  statements taken as a whole. The supplemental  schedule listed in the
Table of Contents is presented for the purpose of additional analysis and is not
a  required  part  of the  basic  financial  statements,  but  is  supplementary
information  required by the  Department  of Labor's Rules and  Regulations  for
Reporting and Disclosure  under the Employee  Retirement  Income Security Act of
1974.  This  schedule  is the  responsibility  of the  Plan's  management.  This
schedule has been subjected to the auditing  procedures  applied in our audit of
the basic 2003 financial statements and, in our opinion, is fairly stated in all
material  respects  when  considered  in  relation  to the basic 2003  financial
statements taken as a whole.


/s/ DELOITTE & TOUCHE LLP

Indianapolis, Indiana
June 16, 2004







EMPLOYEES' THRIFT PLAN OF
INDIANAPOLIS POWER & LIGHT COMPANY

STATEMENTS OF ASSETS AVAILABLE FOR BENEFITS
DECEMBER 31, 2003 AND 2002
------------------------------------------------------------------------------------------------------------------------


ASSETS                                                                                       2003               2002
                                                                                                      
INVESTMENTS--at fair value:
  The AES Corporation Common Stock                                                       $26,103,606        $ 8,065,808
  Merrill Lynch Equity Index Trust--
    Common/Collective Trust                                                                5,061,663          4,181,345
  Merrill Lynch Retirement Preservation Trust--
    Common/Collective Trust                                                                6,165,445          4,215,854
  Aim Income Mutual Fund                                                                     522,737            485,582
  Alliance Technology Mutual Fund                                                          1,130,463          1,134,435
  Ivy International Mutual Fund                                                              643,129            538,193
  Merrill Lynch Balanced Capital Fund                                                      2,452,516          2,094,130
  Merrill Lynch Federal Securities Trust Mutual Fund                                      10,064,764         10,364,771
  Oppenheimer Main Street Income & Growth Mutual Fund                                      8,021,811          6,344,482
  Alger Midcap Growth Institutional Portfolio Mutual Fund                                    282,383
  Templeton Foreign Mutual Fund                                                              680,638
  Van Kampen Growth & Income Mutual Fund                                                     813,480
  Lord Abbett Small Cap Value Mutual Fund                                                    238,786
  JP Morgan Mid-Cap Value Mutual Fund                                                        244,140
  Federated Total Return Bond Mutual Fund                                                    549,830
  Seligman Henderson Global Technology Mutual Fund                                           148,880
  Phoenix Duff & Phelps Real Estate Securities Mutual Fund                                   112,375
  Oppenheimer Real Asset Mutual Fund                                                           8,942
  Franklin Mutual Financial Services Mutual Fund                                              32,931
  Oppenheimer Gold & Special Minerals Mutual Fund                                             44,404
  Delaware Investments Trend Mutual Fund                                                      83,115
  Aim Global Health Care Mutual Fund                                                          36,339
  Merrill Lynch Utility and Telecommunications Mutual Fund                                     6,510
  American Growth Fund of America Mutual Fund                                                653,311
  Participant loans                                                                          601,673
                                                                                         -----------        -----------

           Total investments                                                              64,703,871         37,424,600

CASH                                                                                          96,763              3,312

CONTRIBUTIONS RECEIVABLE                                                                     259,282            222,033

ACCRUED INTEREST AND DIVIDENDS                                                                89,161             88,240
                                                                                         -----------        -----------

ASSETS AVAILABLE FOR BENEFITS                                                            $65,149,077        $37,738,185
                                                                                         ===========        ===========



See notes to financial statements.


EMPLOYEES' THRIFT PLAN OF
INDIANAPOLIS POWER & LIGHT COMPANY

STATEMENT OF CHANGES IN ASSETS AVAILABLE FOR BENEFITS
YEAR ENDED DECEMBER 31, 2003
-------------------------------------------------------------------------------


INCREASES:
  Employee contributions                                           $ 4,299,503
  Company contributions--net                                         2,104,579
  Interest and dividend income                                         750,293
  Net appreciation in fair value of investments                     21,896,725
                                                                   -----------

           Total                                                    29,051,100
                                                                   -----------

DECREASES:
  Withdrawals by participants or their beneficiaries                 1,626,006
  Administrative fees                                                   14,202
                                                                   -----------

           Total                                                     1,640,208
                                                                   -----------

INCREASE IN ASSETS AVAILABLE FOR BENEFITS                           27,410,892

ASSETS AVAILABLE FOR BENEFITS--Beginning of year                    37,738,185
                                                                   -----------

ASSETS AVAILABLE FOR BENEFITS--End of year                         $65,149,077
                                                                   ===========


See notes to financial statements.


EMPLOYEES' THRIFT PLAN OF
INDIANAPOLIS POWER & LIGHT COMPANY

NOTES TO FINANCIAL STATEMENTS
YEARS ENDED DECEMBER 31, 2003 AND 2002
--------------------------------------------------------------------------------


1.   SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

     Basis of Accounting--The financial statements of the Employees' Thrift Plan
     of  Indianapolis  Power & Light  Company (the "Plan") have been prepared on
     the accrual basis.

     Plan  Assets--Assets  of the Plan are  maintained in trust.  Once placed in
     trust,  assets may be withdrawn only for the purpose of refunding  employee
     contributions,  payment  of  vested  employer  contributions  to  employees
     withdrawing   from  the  Plan,   to  employees   obtaining  an   in-service
     (suspension) withdrawal,  to retiring employees, to participants electing a
     loan from the Plan, and to beneficiaries of deceased  employees;  or to pay
     expenses of the Plan. Participants make requests for distributions directly
     with the  recordkeeper,  Merrill Lynch Trust  Company of America  ("Merrill
     Lynch"),  except  for  hardship  withdrawals  and  refunds  of  participant
     contributions,   which  require   approval  from  the  Payroll  &  Benefits
     department of the Indianapolis Power & Light Company ("IPL"). The Payroll &
     Benefits  department of IPL conducts  day-to-day  activities of the Plan at
     the designation of the Employees' Pension & Benefit Committee (the "Pension
     Committee").

     Merrill  Lynch is the sole  trustee and  recordkeeper  of the assets of the
     Plan.

     Investments--Investments   in  securities  are  stated  at  fair  value  as
     determined by quoted market prices. Investment transactions are recorded as
     of the trade  date.  The cost of the  securities  sold is  determined  on a
     specific identification basis.

     Participant   Loans--Loans  to  participants   are  stated  at  cost  which
     approximates fair value.

     Use of Management  Estimates--The  preparation  of financial  statements in
     conformity  with  accounting  principles  generally  accepted in the United
     States of America  requires  that  management  make certain  estimates  and
     assumptions  that affect the reported amounts of assets and liabilities and
     disclosure  of  contingent  assets  and  liabilities  at  the  date  of the
     financial  statements.  The reported  amounts of increases and decreases in
     assets  during the  reporting  period may also be affected by the estimates
     and assumptions  management is required to make.  Actual results may differ
     from those estimates.

     Administrative  Fees--The  Trustee  assesses  each  participant  $1.88 on a
     quarterly basis for the base service fee.  Participants pay a commission of
     $0.08 per share for open market transactions in The AES Corporation ("AES")
     common stock.  The  commission is reflected in the price per share for each
     transaction.  There are no other  transaction-based fees for the investment
     funds.

     Expenses for postage and handling for participant statements, confirmations
     and  distributions  are charged directly to  participants.  It is estimated
     that these expenses will be  approximately  $3.00 per  participant per plan
     year.

     Payment of Benefits--Upon  severance of employment, a participant may elect
     to  receive  a lump sum  payment  for the full  value of the  participant's
     account,  including vested employer contributions and related earnings. The
     participant  also has the option of maintaining  the account until reaching
     the age of 70 1/2 years. Benefits are recorded when paid.

2.   DESCRIPTION OF THE PLAN

     The Plan is administered  by the Pension  Committee which is a committee of
     not less than five  persons  appointed by the IPL Board of  Directors.  The
     Plan is a defined  contribution plan, and certain employees become eligible
     to participate in the Plan immediately upon date of employment.

     All  employees  become  fully  vested  in the  Plan  after  five  years  of
     uninterrupted  service.  Termination  of  employment  before the  five-year
     requirement  requires forfeiture of a prorated amount of allocated employer
     contributions.  Forfeited  amounts may be used to reduce employer  matching
     contributions.  As of December 31, 2003, there is currently  $17,921 in the
     forfeiture fund.

     The Plan is valued on a daily "share" valuation.

     Employee  contributions  are made through payroll  deductions  representing
     amounts  equal to a  specific  percentage  of the  employee's  base rate of
     compensation. Employees have the option of contributing anywhere from 1% to
     50%,  in  increments  of 1%, and  direct  their  contributions  into any of
     twenty-one  options.  Employees can make such contributions under a "Before
     Tax" or "After Tax" option.  Employer  contributions  are made in an amount
     equal to  current  employee  contributions  up to a  maximum  of 4% and are
     invested  in the  same  funds  as  the  employee  elects  to  have  his/her
     contributions  invested.  Prior to February 9, 2002, employer contributions
     were made directly  into the common stock of AES and were not  transferable
     to any of the other funds.  Effective  February 9, 2002,  participants were
     allowed to transfer employer contributions out of the AES common stock fund
     to any of the available  investment  options in accordance  with the Plan's
     procedures.  Effective January 1, 2003, participant  contributions are made
     into the same funds as the participant elects to have his/her contributions
     made into. Each  participant's  account is credited with the  participant's
     contribution and IPL's matching contribution.  Allocations of Plan earnings
     are based on individual account balances relative to total account balances
     as of the valuation dates.

     Participant fund transfers are subject to certain  restrictions as outlined
     in the  Summary  Plan  Description.  In  the  event  of  partial  or  total
     termination  of the Plan,  the funds in the Plan  shall be valued as of the
     date of partial  or total  termination  and,  after  payment  of  necessary
     expenses, shall be distributed as though all participants directly affected
     by the partial or total termination had retired as of that date.

     Participants  may borrow up to the  lesser of 50% of the vested  portion of
     their account or $50,000,  with a minimum loan  requirement of $1,000.  The
     period of repayment of the loan can vary but generally will not exceed five
     years except for loans used to purchase or construct a principal residence.
     The loans are secured by the balance in the participant's  account and bear
     interest at one percent over prime. Principal and interest are paid through
     payroll deductions.

     The Plan is  maintained  with the intent of being a  qualified  trust under
     Section  401(a) of the Internal  Revenue Code.  Its related trust is exempt
     from  Federal  income  taxes  under  Section  501(a) of the Code.  The Plan
     obtained its latest  determination  letter on February 6, 2003 in which the
     Internal  Revenue  Service stated that the Plan, as then  designed,  was in
     compliance with the applicable  requirements of the Internal  Revenue Code.
     The  Plan  has been  amended  since  receiving  the  determination  letter.
     However, the Plan administrator and the Plan's tax counsel believe that the
     Plan,  as amended,  is being  operated in  compliance  with the  applicable
     requirements of the Internal Revenue Code.

     Although it has not  expressed any intent to do so, IPL has the right under
     the Plan to discontinue its  contributions at any time and to terminate the
     Plan subject to the provisions of ERISA. In the event of Plan  termination,
     participants   would   become  100   percent   vested  in  their   employer
     contributions.

     Participants  should  refer  to the  Summary  Plan  Description  for a more
     detailed description of the Plan.

     On June 21,  2001,  the Plan  was  amended  to no  longer  allow  non-union
     employees to make  contributions  to or  participate  in the Plan effective
     July 7, 2001. Effective January 1, 2003, all non-union employees,  who were
     hired  prior  to July 1,  2001,  were  given a  choice  to make a  one-time
     irrevocable election to rejoin the plan.

3.   RISKS AND UNCERTAINTIES

     The  Plan  invests  in  various   securities   including  U.S.   Government
     securities,  corporate  debt  instruments,   corporate  stocks,  registered
     investment companies, and common/collective  trusts. Investment securities,
     in general,  are exposed to various risks,  such as interest rate,  credit,
     and overall market  volatility.  Due to the level of risk  associated  with
     certain investment  securities,  it is reasonably  possible that changes in
     the values of  investment  securities  will occur in the near term and that
     such changes could materially affect the amounts reported in the statements
     of net assets available for benefits.

4.   INVESTMENTS

     The following presents  investments that represent 5 percent or more of the
     Plan's assets.



                                                                                2003               2002
                                                                                          
     The AES Corporation common stock, 2,765,212 and
       2,670,797 shares, respectively                                        $26,103,606        $ 8,065,808*

     Oppenheimer Main Street Income & Growth
       Mutual Fund, 244,567 and 244,019 shares, respectively                 $ 8,021,811        $ 6,344,482

     Merrill Lynch Federal Securities Trust Mutual Fund,
       980,971 and 1,001,427 shares, respectively                            $10,064,764        $10,364,771

     Merrill Lynch Retirement Preservation Trust,
       6,165,445 and 4,215,854 shares, respectively                          $ 6,165,445        $ 4,215,854

     Merrill Lynch Equity Index Trust,
       62,972 and 66,741 shares, respectively                                $ 5,061,663        $ 4,181,345

     Merrill Lynch Balanced Capital Fund
       92,828 and 94,076 shares, respectively**                              $ 2,452,516        $ 2,094,130


     * Includes nonparticipant-directed investments (see Note 2)
     ** 2002 value is over 5%, 2003 value is under 5%


     During 2003, the Plan's investments (including both realized and unrealized
     gains and losses) appreciated in value by $21,896,725 as follows:

        Mutual Funds                                                $ 2,931,347
        Common/Collective Trust                                       1,177,032
        The AES Corporation Common Stock                             17,788,346
                                                                    -----------

        Net appreciation in fair value of investments               $21,896,725
                                                                    ===========

5.   MERRILL LYNCH RETIREMENT PRESERVATION TRUST

     One of the investment  funds is the Merrill Lynch  Retirement  Preservation
     Trust,  which is a trust for the collective  investment of Qualified Plans.
     The majority of the fund assets consist of investment  contracts  which are
     included in the financial  statements at contract value,  (which represents
     contributions made under the contracts, plus earnings, less withdrawals and
     administrative  expenses)  because they are fully benefit  responsive.  For
     example,  participants may ordinarily  direct the withdrawal or transfer of
     all or a  portion  of their  investment  at  contract  value.  There are no
     reserves  against  contract value for credit risk of the contract issuer or
     otherwise.  The contract value of the investment  contracts at December 31,
     2003 and 2002  approximates  market value. The average yield rates for 2003
     and 2002 were approximately 4.26% and 5.47%, respectively.

6.   RELATED PARTY TRANSACTIONS

     Merrill Lynch, the Plan Trustee,  invests in AES common stock. Since AES is
     the parent company of IPALCO Enterprises, Inc. and IPALCO Enterprises, Inc.
     is the parent  company of IPL, any  investment  transactions  involving AES
     common stock qualify as related-party  transactions.  Merrill Lynch is also
     the Investment Manager for the Merrill Lynch Retirement Preservation Trust,
     the Merrill Lynch Equity Index Trust,  the Merrill Lynch  Balanced  Capital
     Fund, the Merrill Lynch Utility and Telecommunications  Mutual Fund and the
     Merrill Lynch Federal Securities Trust.

                                     ******















                              SUPPLEMENTAL SCHEDULE







EMPLOYEES' THRIFT PLAN OF
INDIANAPOLIS POWER & LIGHT COMPANY

FORM 5500, SCHEDULE H, PART IV, LINE 4i--
SCHEDULE OF ASSETS (HELD AT END OF YEAR)
EIN:  35-0413620
PN:  003
DECEMBER 31, 2003
-----------------------------------------------------------------------------------------------------------------------

                                                                                                            Fair
     Shares                                  Description                                  Cost             Value

                                                                                                 
       78,254   Aim Income Mutual Fund                                                 $   538,083      $   522,737
        1,389   Aim Global Health Care Mutual Fund                                          33,553           36,339
       20,807   Alliance Technology Mutual Fund                                          1,968,360        1,130,463
    2,765,212 * The AES Corporation Common Stock                                        51,206,339       26,103,606
       31,159   Ivy International Mutual Fund                                              859,780          643,129
    6,165,445 * Merrill Lynch Retirement Preservation Trust
                  Common/Collective Trust                                                6,165,445        6,165,445
       62,972 * Merrill Lynch Equity Index Trust
                  Common/Collective Trust                                                4,931,739        5,061,663
      244,567   Oppenheimer Main Street Income & Growth Mutual Fund                      8,449,690        8,021,811
      980,971 * Merrill Lynch Federal Securities Trust Mutual Fund                       9,639,115       10,064,764
       92,828 * Merrill Lynch Balanced Capital Fund                                      2,715,500        2,452,516
       63,970   Templeton Foreign Mutual Fund                                              594,967          680,638
       45,093   Van Kampen Growth & Income Mutual Fund                                     726,737          813,480
       18,481   Alger Midcap Growth Institutional Portfolio Mutual Fund                    250,713          282,383
        9,683   Lord Abbett Small Cap Value Mutual Fund                                    221,369          238,786
       13,112   JP Morgan Mid-Cap Value Mutual Fund                                        218,455          244,140
       50,722   Federated Total Return Bond Mutual Fund                                    551,717          549,830
       26,841   American Growth Fund of America Mutual Fund                                583,284          653,311
       12,314   Seligman Henderson Global Technology Mutual Fund                           126,685          148,880
        5,511   Phoenix Duff & Phelps Real Estate Securities Mutual Fund                   101,640          112,375
        1,146   Oppenheimer Real Asset Mutual Fund                                           8,376            8,942
        1,640   Franklin Mutual Financial Services Mutual Fund                              30,557           32,931
        2,123   Oppenheimer Gold & Special Minerals Mutual Fund                             40,773           44,404
        4,407   Delaware Investments Trend Mutual Fund                                      74,510           83,115
          747 * Merrill Lynch Utility and Telecommunications Mutual Fund                     6,129            6,510
                Participant Loans                                                          601,673          601,673
                                                                                       -----------      -----------

                TOTAL INVESTMENTS                                                      $90,645,189      $64,703,871
                                                                                       ===========      ===========



* Party-in-interest transaction





                                   SIGNATURES

     The Plan.  Pursuant to the  requirements of the Securities  Exchange Act of
1934, the trustees (or other persons who  administer the employee  benefit plan)
have  duly  caused  this  annual  report  to be  signed  on  its  behalf  by the
undersigned hereunto duly authorized.


                                EMPLOYEES' THRIFT PLAN OF INDIANAPOLIS POWER &
                                LIGHT COMPANY
                                By the Plan Administrator:


                                EMPLOYEES' PENSION COMMITTEE OF INDIANAPOLIS
                                POWER & LIGHT COMPANY


                                By: /s/ Edward J. Kunz
                                    --------------------------------------------
                                    Edward J. Kunz, Chairman of the Committee





DATE: June 25, 2004