Worldwide, there have been about two dozen airlines go bust so far this year. Most business aviation experts (e.g. those people who've been interviewed on BBC World Service and on the BBC News Channel) estimate that there are about another 30 airlines who'll fail within the next year or so.
Generally, the media refrain from mentioning specific names of the most vulnerable airlines, for fear of being accused of pushing them over the brink. However, the problems of some airlines are well-known. (I was cautioning people about buying tickets with Alitalia, here on AB, many months ago because it was clear that they were about to go bust. It's been announced today that they've no fuel to fly after tomorrow and no money to buy any more).
A BBC News Channel report yesterday cited BA and Ryanair as examples of two airlines which are currently financially secure. (That's because BA's business model, of concentrating on business passengers, seems to be working well, and because Ryanair has simply got plenty of money in the bank).
easyJet's business model seems to meet with the approval of most aviation experts, so they're probably fairly safe at the moment. However I'd not be surprised to see smaller operators, such as FlyBe (and possibly BmiBaby) going out of business in the coming months and years. (FlyBe has seemed to have been struggling almost since the day into came into being).
Of course, the really big question mark must be over the future of ThomsonFly. Like XL, it's an airline which is part of a much bigger holiday group and therefore subject to same sort of financial pressures that resulted in the demise of XL.
Chris