Someone from SilverJet was on Radio 4's Today this morning talking about this. He reckoned that because their market wasn't only City corporates but SMBs and luxury vacationers, they would have a much better chance of survival. They're only a month or two away from break-even, which for a business only a year old is ok. They also structured their prices so that they've been able to hike fares 20% since they started up, without losing any business.
So maybe they'll make it? Good luck to 'em.