Hard to say Grizz. For now it seems to be small regional airlines that were barely making it, a common theme seems to be airlines that were in bankrupcy 2 or so years ago and now are getting cooked.
If I had to make a list of bankruptcy targets I'd say look up a list of any airline that's been in bankruptcy the last 5 years. If they couldn't make it with <$60 oil and cheap credit I'd say they're cooked now.
champion air ceases operations may 31
As for big airlines, they seem to be ok for a little bit, I bet one of them probably isn't but dunno which.
I've heard southwest fluked out on contracts to buy oil for $51 a barrel for 70% of it's oil for 2008, so they've got a year of competitive cost advantage. Every other big airline is getting increasingly fleeced and none of the rest of the big ones will be profitable for 2008. Supposedly 2009 will be do or die time for most of the big guys.
When this is all over there might be some airlines which are real winners too, as they'll be facing a landscape with dramatically less competition. But I think for consumers this will be a bad period, as the days of cheap fares is probably over, and many routes could be cut altogether. Most of the airlines going bankrupt now seem to be the regional ones that made the connecting flights near final destinations. Not clear if those routes will start getting underserved or cut altogether in the future, but possible.
My most favorite airline as a long term winner is TSX:WJA (canadian exchange). Low cost discount provider with satisfied customers, employees with good morale (if I recall they participate in stock programs too), relatively low operational costs, no unions, no debt and paid for planes, and they expand only when they find the cash to pay for it and find a route that's profitable to open. If I recall they just opened a new route from calgary to new york. There are probably good ones in the US somewhere, but I don't know which right now.