In case you’re wondering why airline stocks are taking a dive today, this time the price of crude is not a factor.

Analyst Mike Linenberg at Merrill Lynch issued a downgrade on three of the industry biggies today — US Airways, American Airlines, and Continental Airlines.

Mike downgraded the three to “neutral” from “buy” on valuation concerns, i.e, he thinks they are too expensive.

I don’t disagree. Then again, the valuation issue is just a short-term concern. Longer-term we need to look at where the economy is headed in general for the rest of the year, and that, as I talk about each week, is certainly quite a nebulous thing. Although I think overall we’re still going to see the economy continue to slow down — as the year itself winds down. The only question is how fast the process will move, and if it will gain momentum later in the year — or if it will flatten out before then.