MONTREAL — A new computer problem has been found in the troubled Boeing 737 Max that will further delay the plane’s return to flying after two deadly crashes, according to two people familiar with the matter.

The latest flaw in the plane’s computer system was discovered by Federal Aviation Administration pilots who were testing an update to critical software in a flight simulator last week at a Boeing facility near Seattle, the people said.

Boeing did not immediately respond to a request for comment.

One of the people familiar with the discovery said it would add one to three months to the timetable for returning the Max to flight. Both spoke on condition of anonymity because the development has not been made public.

In response, IATA, which represents hundreds of airlines, pushed again for additional training on the 737. After holding a meeting in Montreal between airlines and regulators, Alexandre de Juniac, head of IATA, said Thursday in a prepared statement that the aviation industry cannot operate effectively without co-ordination between aircraft operators and regulators.

If additional training is required, including the possible introduction of simulators for the Max, it could come at a tremendous cost to Boeing.

Earlier this month Chesley ‘Sully’ Sullenberger, who landed a crippled airliner safely on the Hudson River in 2009, told the House aviation subcommittee that Max pilots should train for emergencies related to flight-control software in simulators – not just on computers, as Boeing proposes. Several others who testified also criticized Boeing’s pilot training for the aircraft, with some saying that Boeing’s zeal to minimize pilot-training costs for airlines buying the 737 Max jet contributed to design errors and inadequate training.

Boeing Co.’s 737 Max fleet has been grounded worldwide after crashes in Indonesia and Ethiopia killed 346 people.

Shares of Boeing fell 2.6% before the market open.

With file from The Associated Press