Filed Pursuant to Rule 424(b)(3)
                                      Registration No. 333-115818

                   PROSPECTUS SUPPLEMENT NO. 4
              TO THE PROSPECTUS DATED JULY 2, 2004
                               OF
                           FLYI, INC.
        (formerly Atlantic Coast Airlines Holdings, Inc.)

                          $125,000,000
                  6% CONVERTIBLE NOTES DUE 2034


  This prospectus supplement relates to resales of our 6%
Convertible Notes due 2034 and shares of our common stock
issuable upon conversion of the Notes, plus an indeterminate
number of additional shares of common stock that may be issued
from time to time upon conversion of the notes as a result of
antidilution adjustments and as additional interest, in
circumstances described in the prospectus to which this
prospectus supplement refers.

  This prospectus supplement, which supplements our prospectus
dated July 2, 2004, contains additional information about the
selling securityholders.

  As used in this prospectus supplement, "the Company," "we,"
"our" or "us" refer to FLYi, Inc. (formerly Atlantic Coast
Airlines Holdings, Inc.) except where the context otherwise
requires or as otherwise indicated.

  You should read this prospectus supplement in conjunction with
the prospectus.  This prospectus supplement updates information
in the prospectus and, accordingly, to the extent inconsistent,
the information in this prospectus supplement supercedes the
information contained in the prospectus.



  Investing in the securities offered in the prospectus involves
risks.  See "Risk Factors" beginning on page 8 of the prospectus.



  Neither the Securities and Exchange Commission nor any state
   securities commission has approved or disapproved of these
   securities or passed upon the adequacy or accuracy of this
 prospectus supplement.  Any representation to the contrary is a
                        criminal offense.





  The date of this prospectus supplement is September 16, 2004



  The information appearing under the section entitled "Selling
Securityholders" beginning on page 44 in the prospectus is hereby
supplemented with the following additional selling securityholder
and footnotes to the table:


                   Principal                 Number of   Percentage
                   Amount of                 Shares of   of Common
                     Notes                   Common      Stock
                   Beneficially  Percentage  Stock That  Outstanding
                   Owned That     of Notes   May Be         (2)
       Name:       May Be Sold   Outstanding Sold (1)



Morgan Stanley & Co.
Incorporated (2A)   7,500,000       6.0%      677,017.5   1.5%(2B)


 *   Less than 1%.

(1)   Assumes conversion of all of the holder's notes at a
   conversion rate of 90.2690 shares of common stock per $1,000
   principal amount of the notes. However, this conversion rate
   will be subject to adjustment as described under "Description
   of Notes - Conversion Rights." As a result, the amount of
   common stock issuable upon conversion of the notes may
   increase or decrease in the future.

(2)   Calculated based on 45,333,810 shares of common stock
   outstanding as of June 30, 2004. In calculating this amount,
   we treated as outstanding that number of shares of common
   stock issuable upon conversion of all of a particular
   holder's notes. However, we did not assume the conversion of
   any other holder's notes.

(2A)  Morgan Stanley & Co. Incorporated was the initial purchaser
   of the notes in February 2004.

(2B)  Morgan Stanley & Co. Incorporated informed us that as of
   September 13, 2004 it beneficially owned an additional
   203,703 shares of Common Stock.  The number of shares in the
   table above does not reflect any sales that may occur of
   other shares beneficially owned by Morgan Stanley & Co.
   Incorporated that are not covered by this prospectus.



  The information referenced below on page 47 in the prospectus
(appearing under the section entitled "Plan of Distribution"), is
hereby amended and restated as follows:

  To our knowledge, Morgan Stanley & Co. Incorporated and
Wachovia Securities International LTD are registered broker-
dealers, and DBAG London, KBC Convertible Mac 28 Fund Ltd, KBC
Convertible Opportunities Fund, KBC Multistrategy Arbitrage Fund,
Melody IAM, Ltd., WPG MSA Convertible Arbitrage Fund, Wachovia
Bank National Association, Deephaven Domestic Convertible Trading
Ltd. and Wachovia Securities International LTD are affiliates of
registered broker-dealers.



                          END OF FILING