XM RADIO CLOSES $250 MILLION INVESTMENT DEAL

Washington D.C., July 08, 1999 -- Washington DC, July 8, 1999, XM Satellite Radio Inc., a subsidiary of American Mobile Satellite Corporation NASDAQ: SKYC), today closed its previously announced investment deal with Clear Channel Communications Inc. (NYSE: CCU); DIRECTV, Inc., a unit of Hughes Electronics Corporation (NYSE: GMH); The General Motors Corporation (NYSE: GM); and a private investment group comprised of Columbia Capital, Telcom Ventures L.L.C. and Madison Dearborn Partners. The combined $250 million is comprised of $75 million each from Clear Channel and the private investment group and $50 million each from General Motors and DIRECTV. American Mobile also completed its acquisition of WorldSpace Inc.'s interest in XM.

XM Satellite Radio (www.xmradio.com) is developing a new band of radio by delivering up to 100 channels of digital-quality audio service with crystal-clear sound from coast to coast directly from its satellites. XM plans to offer subscribers an innovative mix of music, talk, news, sports and entertainment formats for less than $10 a month.

XM is partnering with industry leaders to build its service. Among those companies are General Motors, which will exclusively distribute and market XM service in its vehicles; Alpine, Delphi Delco, Pioneer and Sharp, which will market AM/FM/XM radios; and Hughes and Alcatel, which are building XM's powerful satellites. Owned by American Mobile Satellite Corporation, XM Satellite Radio obtained one of only two satellite digital audio radio service (SDARS) licenses from the Federal Communications Commission in October 1997. First there was AM, then FM and now XM, the next generation of radio.