United Airlines is set to receive a delivery of a 737 Max from Boeing, becoming the first carrier to receive one of the aircrafts since regulators lifted a grounding order in November after 20 months following two fatal crashes.

The lengthy grounding of the aircrafts drove up costs and deprived Boeing of cash, with analysts not expecting the aircraft manufacturer to return to positive free cash flow until the end of 2021.

The Federal Aviation Administration (FAA) last week issued its first airworthiness certificate for a Boeing 737 MAX built since March 2019.

In a statement, United Airlines said it would conduct thorough tests on the aircrafts to determine their safety for passenger use, with pilots also expected to undergo additional training.

"Nothing is more important to United than the safety of our customers and employees, and as we begin receiving 737 MAX deliveries from Boeing, we will inspect every aircraft, require our pilots to undergo additional training reviewed and approved by the FAA, and conduct test flights before we bring these aircraft back into service," said United.

There have been 565 cancellations of 737 MAX jets from March 2019 through to October this year.

The announcement by United Airlines comes following another last week which noted Irish airline Ryanair had signed a deal to acquire 75 of the planes.

(With input from agencies)