Southwest Airlines said Monday it would speed up inspections on 38 airplanes it bought from foreign air carriers after regulators threatened to ground the jets because they might not meet federal aviation safety requirements.

The inspections will be completed by Jan. 31, five months sooner than planned, according to documents released Monday by the Senate Commerce Committee.

The planes are among 88 used Boeing 737 aircraft that Southwest bought from 2013 to 2017 from 16 foreign carriers. The speedier checks come after inspections of some of the used planes turned up previously undisclosed repairs and incorrectly completed fixes. Southwest used multiple contractors to conduct reviews of the planes’ maintenance records when it bought the planes.

Southwest sought to play down the inspections. “Our actions did not stem from any suspected safety concerns with the aircraft but were an effort to reconcile and validate records and previous repairs,” the airline said in a statement.