DALLAS - Tens of thousands of business trips and vacations were disrupted Wednesday as American Airlines canceled more than 1,000 flights -- nearly half its schedule -- to fix faulty wiring that could cause a short-circuit or even a fire and explosion.

The airline said it expected to cancel 900 more flights today.

It was the latest -- and largest -- in a wave of cancellations at major U.S. airlines that have caused long lines at ticket counters and made flying even more stressful than usual.

American canceled 13 departures from Minneapolis-St. Paul International Airport Wednesday, all related to the inspection issues. Eight of the flights were to Chicago, three to Dallas-Fort Worth and two to LaGuardia Airport in New York, said spokesman Tim Loecker in Dallas. No stop-over flights were stranded at Minneapolis-St. Paul, he said.

Executives at American said safety never was compromised, and they suggested that the nation's biggest airline was the victim of suddenly increased scrutiny by federal regulators.

American estimated that more than 100,000 travelers were booked on Wednesday's 1,094 canceled flights. Many had to scramble to book new flights and were stranded at hotels far from home. The airline already had canceled 460 flights Tuesday after federal inspectors found problems with wiring work done two weeks ago in a first set of shutdowns.

A top executive said the cancellations would be a "significant" cost to American, and shares of parent AMR Corp. fell 11.1 percent, down $1.15 to $9.17.

The issue stems from a September 2006 order by the Federal Aviation Administration (FAA) -- which airlines had until last month to meet -- about bundling of wires in the MD-80 fuel-pump backup power system. The fear is that improperly bundled wires could rub, leading to an electrical short or even fire. However, no serious incidents have been blamed on the bundles, the FAA said.

American officials thought they'd fixed the problem last month. But this week, FAA inspectors found problems with the work done on more than a dozen airplanes. American said it had no choice but to ground all 300 of its MD-80s to deal with the wiring bundles.

American operates about 2,200 daily flights, more than one-third with MD-80s, a longer, improved version of the two-engine DC-9. Nearly half the cancellations were concentrated at two airports, in Dallas and Chicago.

Staff writer Steve Alexander contributed to this report.