United Airlines has announced a timeframe to fly the Boeing 737 MAX again, saying the jet would resume flights in February.

Boeing 737 MAX, which was out of service for 20 months following two fatal crashes, will re-enter United’s schedule on February 11, with service from Denver and Houston.

This is after the Federal Aviation Administration’s November decision to permit the jet to fly again following upgrades to its software and new protocols on pilot training.

United said there was still additional work to do on its jets before they can return to service with the carrier.

The two 737 MAX crashes, in Ethiopia and Indonesia, claimed 346 lives and led to its worldwide grounding.

“Nothing is more important to United than the safety of our customers and employees,” a United spokesman said.

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“United’s MAX fleet won’t return to service until we have completed more than 1,000 hours of work on every aircraft, including FAA-mandated changes to the flight software, additional pilot training, multiple test flights and meticulous technical analysis to ensure the planes are ready to fly.”

United said it would be “fully transparent” with customers and will rebook or refund customers who don’t want to fly on the aircraft.

The MAX returned to commercial service on December 9 following an uneventful flight on low-cost Brazilian carrier Gol.

In the United States, American Airlines is scheduled to resume flights on the MAX later this month.