October 8, 2001 Rare Medium Group, Inc. 565 Fifth Avenue 29th Floor New York, NY 10017 Attention: General Counsel RE: Letter Agreement Ladies and Gentlemen: Reference is hereby made to the letter agreement dated October 1, 2001 by and among Motient...

                                 EXHIBIT 10.54b

                               Motient Corporation
                              MR Acquisition Corp.
                              00000 Xxxxxxxxx Xxxx.
                           Xxxxxx, Xxxxxxxx 00000-0000




                                 October 8, 2001





Rare Medium Group, Inc.
000 Xxxxx Xxxxxx
00xx Xxxxx
Xxx Xxxx, XX 00000
Attention:  General Counsel

                           RE:      Letter Agreement

Ladies and Gentlemen:

     Reference is hereby made to the letter  agreement  dated October 1, 2001 by
and among Motient Corporation ("Acquiror"),  MR Acquisition Corp. ("Merger Sub")
and Rare Medium  Group,  Inc.  (the  "Company,"  which,  along with Acquiror and
Merger Sub, is sometimes  hereinafter referred to collectively as the "Parties")
(the "Letter Agreement").

     The Parties  hereby  acknowledge  and agree that the date  "October 8, 2001
wherever  it appears in the Letter  Agreement  is amended to read  "October  12,
2001."

     Except as expressly  modified by this  amendment,  the Letter  Agreement is
hereby  ratified and confirmed  and shall remain in full force and effect.  This
amendment may be executed and delivered in two or more counterparts,  and by the
different Parties hereto in separate  counterparts,  each of which when executed
and delivered  shall be deemed to be an original but all of which taken together
shall constitute one and the same amendment.

     This amendment shall be governed by, and construed in accordance  with, the
laws of the State of Delaware  without  regard to any principles of conflicts of
law.

     Please  acknowledge your  understanding of and agreement with the foregoing
by signing this amendment in the space provided below.

                          Sincerely,

                          MOTIENT CORPORATION


                          By:/s/Xxxxxx X. Xxxxxxx, Xx.
                             -------------------------
                          Name:  Xxxxxx X. Xxxxxxx, Xx.
                          Title:  President and
                                  Chief Executive Officer

                          MR ACQUISITION CORP.


                          By:/s/Xxxxxx X. Xxxxxxx, Xx.
                          Name:  Xxxxxx X. Xxxxxxx, Xx.
                                 ----------------------
                          Title:  President


AGREED TO AND ACCEPTED
This 8th day of October, 2001

RARE MEDIUM GROUP, INC.


By:/s/Xxxxx Xxxxxx
------------------
Name:  Xxxxx Xxxxxx
Title:  Chairman and
        Chief Executive Officer