FORT WORTH (CBSDFW.COM) – Yet another delay for the return of the Boeing 737 Max jets. American Airlines announced that is extending cancellations of flights on the aircrafts until at least June.

The Fort Worth-based airline said Tuesday it is pulling the troubled planes from the schedule until June 4 and cancelling nearly 20,000 flights. American had previously canceled service on the jets through April 6.

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Recently Boeing recommended that all pilots take simulator training before resuming flying the planes. Ironically, a lack of simulator training was a key selling point to airlines when originally shopping the 737 Max.

American Airlines had 24 Boeing 737 Max aircraft in its fleet when the planes were grounded — and had contracted for 40 more. In October the airline estimated the removal of the Max from the air cost the company some $540 million in pretax income last year.

Whenever American returns the 737 Max jets to the air the company says they will “gradually phase in the MAX for commercial service and will increase flying on the aircraft throughout the month.”

The 737 Max was grounded worldwide in March 2019 after deadly crashes involving the plane model in Ethiopia and off the coast of Indonesia, which occurred within five months of each other. A total of 346 people lost their lives.

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Before being grounded Boeing had built and delivered some 400 Max jets to airlines.