There is enough coverage of this already, but essentially Silverjet has been crippled by the rising cost of fuel, and the unwillingness of investors to throw money into the airline industry at a time of recession. The supply of cheap(in price and quality) business class seats to New York also increased from 1 April when the limits on the numbers of US airlines that could fly Heathrow to the USA were lifted, and Delta and Continental stepped in. They benefit from large domestic feeder networks in the USA (and linkages with Skyteam airlines Air France, KLM and Alitalia). Silverjet had no feeders.
Maxjet, EOS and Silverjet were all three all business class airlines flying from London (Stansted the first two and Luton for Silverjet) to New York (Dubai also for Silverjet). L'Avion remains flying from Paris to NY, and both Lufthansa and Singapore Airlines operate all business class flights of their own (and BA will be doing so from next year). The business model isn't wrong, it's just the airline business is difficult, requires network economics, and access to the most lucrative airports - in that respect, all three startups lacked the capital to fight it out in difficult times.
Meanwhile, it's cheap to fly Trans Atlantic in economy, premium economy and business class - still!
