Alaska Airlines has begun flying Boeing 737 Max 9 planes again after being grounded after a panel exploded on the side of one of the airline’s planes, causing a door to come off. The airline said in a statement that it has completed its final inspection of its aircraft group. They said they resumed Max 9 flights with a flight from Seattle to San Diego on Friday afternoon.

On Wednesday, the Federal Aviation Administration, which also called for the review of another plane model, approved the inspection and maintenance process to get the planes flying again. Alaska technicians began inspections that night, the airline said. They expect inspections to be completed by the end of next week, allowing the airline to operate a full flight schedule.

The head of Boeing’s commercial aircraft division apologized in a message to employees Friday afternoon for the American manufacturer’s latest setbacks as the 737 MAX 9 returns to the air. “We are very sorry for the significant disruption and frustrations to our customers,” Stan Deal said in a message to his employees sent by Boeing to the press.

Inspections can take up to 12 hours per plane. “Each of our 737-9 MAX will return to service only after rigorous inspections are completed and each aircraft is deemed fit to fly in accordance with FAA requirements,” the airline said in a written statement on Friday. United intends to do the same on Sunday, but a spokesperson said the airline could use them as spare planes on Friday or Saturday.

Alaka Airlines and United are the only two US airlines that operate this particular model of the Boeing 737. The Federal Aviation Administration has detailed the process that airlines must follow to inspect, and if necessary, repair, panels called door plugs, one of which was released on Alaska Airlines Flight 1282 on January 5. The plugs are used to seal the holes left for additional doors in the Max 9 when an unusually high number of seats requires more exits for safety reasons.

Separately, United Airlines said it had resumed using its Boeing 737 MAX 9 planes this Saturday for passenger flights after US regulators gave the green light following a mid-air cabin explosion on an Alaska Airlines flight. earlier this month.

On Wednesday, the FAA lifted its grounding order by approving new inspections and maintenance checks and said Boeing could not expand 737 MAX production or add new 737 production lines pending quality improvements.

The 737 MAX 9 enhanced maintenance process requires inspection of specific bolts, guides and hardware along with detailed visual inspections of mid-cabin exit door plugs and dozens of related components.

Alaska Airlines grounded its 65 Max 9 planes just hours after one of two door plugs in the rear half of Flight 1282’s cabin exploded while it was 16,000 feet (about 4,900 meters) over Oregon. The FAA grounded all Max 9s in the US the day after the explosion. No passengers were seriously injured. As a result of the incident, Boeing suffered stock market declines.