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:

              Mid-America Energy Resources Employee Retirement Plan

     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




MID-AMERICA ENERGY RESOURCES
EMPLOYEE RETIREMENT PLAN

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

                                                                                                          Page
FINANCIAL STATEMENTS (Unaudited):

                                                                                                        
     Statements of Assets Available for Benefits
           as of December 31, 2003 and 2002 (Unaudited)                                                    1

     Statements of Changes in Assets Available for Benefits
           for the Year Ended December 31,2003 (Unaudited)                                                 2

     Notes to Financial Statements                                                                         3

     * 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.







MID-AMERICA ENERGY RESOURCES
EMPLOYEE RETIREMENT PLAN

STATEMENTS OF NET ASSETS AVAILABLE FOR BENEFITS
--------------------------------------------------------------------------------------------------------------


                                                                                 2003                 2002
                                                                               Unaudited            Unaudited
                                                                                                 
ASSETS:

INVESTMENTS - at fair value:

  The AES Corporation
    Common Stock                                                                  84,142               32,844

  Merrill Lynch Equity Index Trust Fund
    Common/Collective Trust                                                      219,354              175,636

  Merrill Lynch Retirement Preservation Trust Fund
    Common/Collective Trust                                                      103,940              101,074

  Oppenheimer Main Street & Growth
    Mutual Fund                                                                  124,394              124,724

  Ivy International Fund
    Mutual Fund                                                                    6,752                5,308

  Aim Income Fund
    Mutual Fund                                                                    3,014                2,729

  Merrill Lynch Global Allocation Fund
    Mutual Fund                                                                  347,886              260,479

  Merrill Lynch Balanced Capital Fund
    Mutual Fund                                                                  121,662              104,619

  Participant Loans                                                                3,558                6,132
                                                                           --------------       --------------

           Total Investments                                                   1,014,702              813,545

CASH                                                                                   -                    -

CONTRIBUTIONS RECEIVABLE                                                               -                    -

ACCRUED INTEREST AND DIVIDENDS                                                     1,953                1,939
                                                                        -----------------    -----------------

     Total assets                                                              1,016,655              815,484
                                                                        -----------------    -----------------

LIABILITIES:

ACCRUED Fees                                                                           -                1,065

                                                                        -----------------    -----------------
     NET ASSETS AVAILABLE FOR BENEFITS                                   $     1,016,655      $       814,419
                                                                        =================    =================




See notes to financial statements.



MID-AMERICA ENERGY RESOURCES
EMPLOYEE RETIREMENT PLAN


STATEMENTS OF CHANGES IN ASSETS AVAILABLE FOR BENEFITS
FOR THE YEAR ENDED DECEMBER 31, 2003 (Unaudited)
------------------------------------------------------------------------------

INCREASES

Employee contributions                                        $             -
Company contributions, net                                                  -
Interest and dividend income                                           19,895
Rollover accounts and principal repayments                              1,066
Net appreciation (depreciation) of investments                        260,464
                                                              ----------------
          Total                                                       281,425
                                                              ----------------

DECREASES

Withdrawals by participants or their
  beneficiaries                                                        79,189
Loan repayments from distributions                                          -
Administrative fees                                                         -
                                                              ----------------
          Total                                                        79,189
                                                              ----------------

DECREASE IN ASSETS AVAILABLE FOR BENEFITS                             202,236

ASSETS AVAILABLE FOR BENEFITS, BEGINNING OF YEAR                      814,419

                                                              ----------------
ASSETS AVAILABLE FOR BENEFITS, END OF YEAR                    $     1,016,655
                                                              ================



See notes to financial statements.

MID-AMERICA ENERGY RESOURCES
EMPLOYEE RETIREMENT PLAN


NOTES TO FINANCIAL STATEMENTS


1.   SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

     Basis of Accounting

     The  financial  statements of the  Mid-America  Energy  Resources  Employee
     Retirement Plan (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, payment to employees  obtaining an in-service  distribution,  payment
     due to a  hardship  withdrawal,  issuing  loan  proceeds,  distribution  to
     retiring employees,  distribution to beneficiaries of deceased employees or
     to pay expenses of the Plan.  All payments  made from the trust require the
     approval of the Employee's  Pension Committee of Indianapolis Power & Light
     Company, Inc. (the "Pension Committee"). Merrill Lynch Trust Company is the
     sole Trustee and record keeper 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.
     Cost of 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  generally
     accepted  accounting  principles  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 net 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.

     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.

     Administrative Fees

     For the plan  year  ended  December  31,  2003,  each  participant  with an
     investment in the AES Common Stock Fund was charged  approximately $.08 per
     share. There are no other  transaction-based  fees for the other investment
     funds.  Administrative fees on the mutual and managed funds were based upon
     fund balances.


2.   DESCRIPTION OF THE PLAN

     The Plan is  administered  by the  Pension  Committee  which is a committee
     appointed by the  Indianapolis  Power & Light Company  ("IPALCO")  Board of
     Directors.  The Plan is a defined  contribution plan, and employees of MAER
     and its affiliates become eligible to participate in the Plan at attainment
     of age 18 and immediately upon hire.

     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.

     Employee  contributions  are made through payroll  deductions  representing
     amounts  equal to a specified  percentage  of the  employee's  base rate of
     compensation. Employees have the option of contributing anywhere from 1% to
     15% in increments of 1%. Employer contributions are made in an amount equal
     to current employee contributions up to a maximum of 6%. Each participant's
     account is credited with the participant's contribution and MAER'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.

     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 November 14, 1995 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.

     Participants  may obtain a loan from the Plan up to a maximum of the lesser
     of $50,000 or one-half of the participant's vested account balance (subject
     to the  provisions of the Plan).  Each  participant  may have only one loan
     outstanding  at any time.  Loans are to be repaid over a term not to exceed
     five  years.  Loans bear an interest  rate as outlined in the Summary  Plan
     Description.

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

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


                                                                       2003                2002
                                                                                      
     The AES Corporation common stock 8,913 and
       10,875 shares, respectively                                      84,142              32,844

     Oppenheimer Main Street Income & Growth
       Mutual Fund, 3,793 and 4,797 shares, respectively             $ 124,394           $ 124,724

     Merrill Lynch Global Allocation Fund
       23,177 and 22,789 shares,
        respectively                                                 $ 347,886           $ 260,479

     Merrill Lynch Retirement Preservation Trust,
       103,940 and 101,074 shares, respectively                      $ 103,940           $ 101,074

     Merrill Lynch Equity Index Trust,
         2,729 and 2,803 shares, respectively                        $ 219,354           $ 175,637

     Merrill Lynch Balanced Capital Fund
          4,605 and 4,700 shares, respectively                       $ 121,662           $ 104,619




     During 2003, the Plan's investments (including both realized and unrealized
     gains and losses) appreciated in value by $260,464 as follows:


          Mutual Funds                                           $  131,307
          Common/Collective Trust                                    49,150
          Common Stock                                               80,007
                                                                 ----------
          Net depreciation in fair value of investments          $  260,464
                                                                 ==========


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  Mid-America  Energy  Resources,  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 Global  Allocation  Fund,  and the Merrill Lynch Balanced
     Capital Fund.

                                    * * * * *



                                   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.


                                   MID-AMERICA ENERGY RESOURCES EMPLOYEE
                                   RETIREMENT PLAN
                                   By the Plan Administrator:


                                   EMPLOYEE'S PENSION COMMITTEE OF INDIANAPOLIS
                                   POWER & LIGHT COMPANY


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





DATE: June 25, 2004


                              REQUIRED INFORMATION


     The  certification  of the chief executive  officer and the chief financial
officer of IPALCO Enterprises,  Inc., pursuant to 18 U.S.C.ss.1350,  is attached
hereto as Exhibit 99.