After American Airlines (AA) grounded a large part of its fleet and canceled more than 2,400 flights since Tuesday, it was Midwest Airlines’ turn to do it. The Milwaukee-based air carried grounded 13 jets for re-inspections to the wiring harness - the same reason AA canceled flights.

Midwest Airlines announced that it has made the cancellations voluntarily. It grounded 13 Boeing MD-80 airplanes to make sure that the wiring harness is in conformity with the directive released by the Federal Aviation Administration (FAA).

According to the Midwest spokesman Mike Brophy, the MD-80s were ok, but the management decided the company’s own personnel should re-inspect the aircrafts.

Midwest Airlines only said it canceled 10 flights by Thursday morning, but couldn’t estimate how many would follow.

American Airlines executive vice president Daniel Garton said the mass cancellations could continue on Friday and the return to a normal schedule depends on how quick the mechanics carry out the inspections and the eventual repairs of the wire bundles.

On late Wednesday afternoon, 60 planes were cleared for flight, 119 were under inspections and repairs and 121 were expecting inspection, said AA spokesman Tim Wagner.

The aircrafts went through another inspection and fixing period two weeks ago, but when the FAA inspectors conducted another survey they found out that 15 of 19 American jets they examined flunked. The findings of FAA’s survey left AA management with no choice but to ground all 300 of its MD-80s. American Airlines has a fleet of 655 planes.

"We have obviously failed to complete the airworthiness directive to the precise standards that the FAA requires, and I take full responsibility for that," said Gerard Arpey, AA's chairman and chief executive.