Boeing faces a crucial test this week as global regulators meet in Texas to determine when the grounded 737 Max aircraft will return to the air, after further revelations of problems with software used to train pilots to fly the aircraft.

The world’s largest commercial aircraft manufacturer revealed at the weekend that it had been forced to correct a flaw in the software of flight-training simulators that are meant to reproduce the flying conditions of the Max aircraft involved in two deadly crashes in the past six months.

The disclosure is a further blow to Boeing’s credibility, which has been seriously damaged by the two crashes, in which 346 people died. Subsequent disclosures of serious design flaws both in the Max’s anti-stall system, called the manoeuvring characteristics augmentation system (MCAS), and errors involving other safety systems have further undermined the reputation of the Chicago-based company.