Either the Federal Aviation Administration is on the warpath, or our nation's carriers desperately need to refresh their fleets.

Earlier today, American Airlines parent AMR (NYSE: AMR) grounded 200 flights after regulators, following a maintenance audit, raised questions about the wiring in its fleet of MD-80 aircraft. It's the second time in a week that American has canceled flights because of maintenance issues.

The MD-80 is a medium-range aircraft based on the original McDonnell-Douglas DC-9, which was first introduced in 1965. Boeing (NYSE: BA), which acquired McDonnell-Douglas in 1997, no longer manufactures new models of the MD-80.

Don't overlook that last point; it's crucial. Why? The FAA is very likely citing old jets. Not long ago, Southwest's (NYSE: LUV) aging fleet of 737 aircraft caught regulators' eye.

Who's next? Delta (NYSE: DAL)? Alitalia? SAS? All three fly the MD-80.

We don't know, of course. We do know that, because Southwest flies the 737 and faces its own set of maintenance concerns, these issues aren't exclusive to aircraft. And that means any carrier -- Northwest (NYSE: NWA), JetBlue (Nasdaq: JBLU), UAL (Nasdaq: UAUA) -- could be next.

So, let's not pick on American too much. If the pattern holds -- and, in investing, it usually does -- there's plenty of finger-pointing still to come.

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Fool.com and Rule Breakers contributor Tim Beyers owned shares of Southwest at the time of publication. You can find Tim's portfolio here and his latest blog entry here. The Motley Fool's disclosure policy has cleared your portfolio for takeoff.