FORT WORTH, Texas (AP) — American Airlines is closing its pilot base in St. Louis, one more disappearing vestige of the carrier's takeover of once-proud TWA nearly two decades ago.

American announced Monday that starting next September the 180 pilots based in St. Louis will have to move or commute to assignments — not unusual in the airline business — if they want to keep their jobs.

The move comes as American retires TWA's old MD-80 planes and replaces them with Boeing 737s.

TWA was an iconic name in aviation, but after years of decline it went into bankruptcy protection. That's when Fort Worth-based American bought it in 2001.

TWA had 2,300 pilots at the time. American says 1,000 remain; many of the others hit retirement age.