Southwest said Thursday that a fifth plane with cracks in the skin will be held back for additional, previously scheduled maintenance.
The airline grounded 79 of its older Boeing 737 aircraft for inspections after a hole opened in the roof of a similar plane over Arizona last week, forcing an emergency landing.
Southwest, which has more than 540 planes, said it was operating a normal schedule of about 3,400 flights on Thursday.
Boeing Co. gave Southwest instructions for repairing the cracked planes. The airline’s mechanics were replacing an 18-inch section of the roof on each, a job that takes one to two days.
The 15-year-old 737-300 plane with a hole in the roof was outfitted with a large green aluminum patch in the roof while it sat on the tarmac at a military base in Yuma, Ariz., where it landed last Friday. Southwest said the plane will be flown to a maintenance center for permanent repairs once Boeing determines how to do the job.
National Transportation Safety Board investigators took a chunk of roof around the 5-foot-long hole to Washington this week to analyze why it came apart along a joint formed by two overlapping aluminum panels.
After last week’s mishap, the Federal Aviation Administration ordered airlines to conduct detailed inspections of the same area on certain models of older 737s that have made at least 30,000 flights, and to inspect them again every 500 flights. Southwest has nearly 80 planes covered by the order.