I'm sitting in the terminal in OKC and they just announced that the American Airlines MD-80 fleet is grounded, at least for today and possibly into tomorrow.
I'm not sure why, and researching more potential links.
MD-80s are the majority of American's domestic fleet, and disgruntled passengers are filing by me (as I wait for my crappy CRJ flight on Northwest) up to the ticketing counter to be rebooked on other airlines.
With the recent 737 grounding at Southwest, this is a bit scary. Interesting to see if DC-9s go next.
Update - Apparently this is a continuing saga. AA and Delta had numerous cancellations of MD-80 flights in late March to conduct inspections.