Failings by pilots during simulator tests have led US regulators to consider introducing additional training for flight crews on the 737 Max.
In a letter to Boeing, the Federal Aviation Administration (FAA) said additional tests were needed after pilots made multiple mistakes while responding to simulated emergencies during sessions in December.
The simulations replicated failures similar to those in two fatal crashes which led to the worldwide grounding of Boeing’s Max.
In the letter, seen by Bloomberg, the FAA said that the results may prompt “additional training requirements pertaining to the” aircraft.
There is no indication yet that the need for additional training would delay the Max’s return to service, but more training requirements could be costly for airlines.
The jet has faced a number of complications to its return to service, including issues with software and a debate over the level of training pilots require.
In a statement issued to Bloomberg, Boeing said: “We have submitted an initial recommendation regarding simulator training on the 737 Max, but we will continue to work with airline customers and global regulators to assess and finalize the content of the training.”
It added: “Ultimately, it will be the regulators who determine the training requirements.”
During the December sessions, pilots from a number of American airlines were assessed on Boeing’s updated flight control system.
According to the letter from the FAA, while the crews’ mistakes during simulations did not lead to crashes, the errors were extensive enough to warrant concern among regulators.
The pilots had reportedly the received additional training proposed by Boeing but still failed to complete emergency checklists related to the Maneuvering Characteristics Augmentation System.Assessed pilots also had difficulty with emergency procedures related to sensor failures and erroneous instrument readings, according to the letter.