DALLAS (AP) — Federal officials in the United States (US) said on Friday they are investigating after a crack ruptured the skin on a Boeing 737 jet operated by Southwest Airlines, causing the plane to gradually lose cabin pressure. The incident occurred on Monday on a flight from Las Vegas to Boise, Idaho. Flight records show that the pilots began a rapid, six-minute descent from 39,000 feet to 22,000 feet.
At that altitude, the cabin pressure was safe, and the crew completed the flight, said Southwest and the Federal Aviation Administration (FAA). Oxygen masks in the passenger cabin never dropped from the ceiling, and no injuries were reported, the airline and the regulatory agency said.
The FAA said that an inspection turned up a 12-inch crack in the skin of the plane’s crown behind the cockpit. Airlines are required to inspect that area every 1,500 flights. The FAA said it was too early to know whether the frequency of inspections should be increased.
Southwest spokeswoman Michelle Agnew said the plane had been inspected for cracks within the required 1,500-flight period.
Agnew said that during the flight, pilots responded to an indicator in the cockpit and “followed standard procedures by descending to a lower altitude to maintain a safe and comfortable cabin environment.” That “resolved the issue,” and the crew continued safely to Boise, she said.
“The aircraft did not incur a rapid depressurisation, masks were not deployed, and the aircraft did not require a diversion to maintain safety of flight,” Agnew said. On Friday, the plane was in a maintenance facility and undergoing repairs for the crack, she said.
A spokesman for Chicago-based Boeing said the manufacturer was aware of the incident and was working with Southwest to learn more.
The incident was reported earlier by The Wall Street Journal.
The newspaper, citing people familiar with the matter, said Southwest told the FAA that required inspections turned up external cracks in two other planes in the same area but that those incidents didn’t lead to cabin decompression.
Breaks in the skin of aluminium-body jets such as the Boeing 737 are usually caused by fatigue or wear and tear.