It’s Friday. Do you know how well YOUR favorite airline did for the first quarter of 2009?

As of today, all the major airlines have reported earnings.

So what have we learned? A couple of things.

One, Allegiant Air continues to blow away everybody else on the block. The travel company, which happens to include an airline that happens to fly only MD-80s that also happens to make money hand over fist had a spectacular first quarter. As I mentioned earlier this week, a 31.3% operating margin was posted by the airline.

You just don’t see margins like that in this industry.

I told you guys not to believe that anti-Allegiant rant that CNBC’s Jim Cramer spewed out not too long ago. Cramer, by lumping ALGT with Las Vegas “casino stocks,” proved that his research is lacking.

We also learned this week that AirTran had a great first quarter. No, the results were not as stratospheric as those of Allegiant, but they were pretty damn good. Nice fat profit, and nice big declines in costs. Excellent job.

We also learned that while we may have hit a point where declines in demand have more or less leveled out — nobody, and I mean, NOBODY, (well, except for Allegiant) is ready to call what is going to happen in May and June.

Preliminary bookings are down — but will they recover, as more and more passengers continue to book tickets closer in? Then again, at the heart of the demand decline here in the U.S. is the declining number of premium passengers. That is only going to improve when the economy improves.

What I might have concerns about if I were an airline other than Allegiant is just how much of that previous business travel my airline had before does return. Even if the economy picks up.

You don’t have to look very far to see what is happening in companies both big and small these days. Companies are cutting back on travel and are using video conferencing more and more. Heck, today anyone with a laptop can connect via video to a small one-on-one meeting or to a meeting with many more participants. There is no question that the quality and ease, not to mention the low to no-cost of such efforts — has changed dramatically just in the last couple of years.

So yes, I am concerned that going forward — if a company gets used to using video conferencing as a result of the current belt-tightening — is that same company going to be anxious to start spending money on sending their employees to far-flung regions of the country? Much less the rest of the world? Just because they now have a little extra money to spend?

I’m not so sure.

And, if this is the case — which airlines stand the best chance of inheriting the earth? Or at least the bulk of the shorter-term profit kitty? Those airlines that cater to the leisure traveler and have the low fares and low cost structure to make money doing so.

Which is one of the reasons why Morgan Stanley analyst Bill Greene recently advised airline stock investors to move out of U.S. legacy carriers and into low cost, low fare airlines such as Allegiant, AirTran and JetBlue. US Airways kind of sneaks in there as well, as it has the lower fares and the lower cost structure and a bigger domestic market than that of American, United, Delta, or Continental.