Boeing Co.’s 737 Max program had been a financial star with more than 5,000 orders, but two deadly crashes in five months have raised questions about whether the U.S. aircraft maker has done enough since the plane’s introduction in 2017 to ensure pilots receive sufficient training.

Boeing and long-time European competitor Airbus SE have been competing fiercely for sales. The American manufacturer has also been under pressure to co-ordinate with airlines to improve training for less-experienced pilots to handle the complexities of the new Max configuration of the 737, industry experts say.

“There’s a shared responsibility with the manufacturer and airline to make sure that pilots are adequately trained, but once they know there’s a problem, airlines look to Boeing to tell them what the issue is,” said veteran aviation observer Karl Moore, a professor at McGill University’s Desautels Faculty of Management. “There has been a long evolution of the 737 over many decades with new technology brought on board and, to a considerable degree, advanced avionics.”

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key feature of boeing max The Boeing 737 Max incorporates the Maneuvering Characteristics Augmentation System (MCAS) – an anti-stall feature introduced to compensate for the heavier engines, which changed the aerodynamics of the jet, tending to push the nose of the aircraft up HOW MCAS WORKS AOA sensor Winglet aligns itself with airflow Level flight: Normal angle of attack (AOA) – angle at which airflow hits aircraft Aircraft trajectory Air flow CFM Leap-1B turbofan Nose-up flight A high AOA puts aircraft at risk of stalling. MCAS is automatically triggered, moving the horizontal stabilizer trim counterclockwise, which pushes the jet’s nose down Longitudinal axis of aircraft Angle of attack Aircraft trajectory Air flow Measured angle of attack System activates only when plane is being flown manually, in flaps-up flight, and typically during steep turns the globe and mail, Sources: graphic news; AP; JAO Aero Media LLC; the New York Times; Seattle Times; the air current key feature of boeing max The Boeing 737 Max incorporates the Maneuvering Characteristics Augmentation System (MCAS) – an anti-stall feature introduced to compensate for the heavier engines, which changed the aerodynamics of the jet, tending to push the nose of the aircraft up HOW MCAS WORKS AOA sensor Winglet aligns itself with airflow Level flight: Normal angle of attack (AOA) – angle at which airflow hits aircraft Aircraft trajectory Air flow CFM Leap-1B turbofan Nose-up flight A high AOA puts aircraft at risk of stalling. MCAS is automatically triggered, moving the horizontal stabilizer trim counterclockwise, which pushes the jet’s nose down Longitudinal axis of aircraft Angle of attack Aircraft trajectory Air flow Measured angle of attack System activates only when plane is being flown manually, in flaps-up flight, and typically during steep turns the globe and mail, Sources: graphic news; AP; JAO Aero Media LLC; the New York Times; Seattle Times; the air current key feature of boeing max The Boeing 737 Max incorporates the Maneuvering Characteristics Augmentation System (MCAS) – an anti-stall feature introduced to compensate for the heavier engines, which changed the aerodynamics of the jet, tending to push the nose of the aircraft up HOW MCAS WORKS AOA sensor Level flight: Normal angle of attack (AOA) – angle at which airflow hits aircraft Winglet aligns itself with airflow Aircraft trajectory CFM Leap-1B turbofan Nose-up flight A high AOA puts aircraft at risk of stalling. MCAS is automatically triggered, moving the horizontal stabilizer trim counterclockwise, which pushes the jet’s nose down Longitudinal axis of aircraft Angle of attack Aircraft trajectory Air flow Measured angle of attack System activates only when plane is being flown manually, in flaps-up flight, and typically during steep turns the globe and mail, Sources: graphic news; AP; JAO Aero Media LLC; the New York Times; Seattle Times; the air current

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Prof. Moore made the comments on Wednesday, three days after a Max 8 operated by Ethiopian Airlines crashed shortly after takeoff from Addis Ababa on a flight bound for Nairobi, killing 157 people, including 18 Canadians. In October, 189 people died when a Max 8 flown by Lion Air of Indonesia plunged into the Java Sea soon after departing from Jakarta on a short-haul flight.

On Wednesday, Canada and the United States grounded Max aircraft. More than 40 other countries had already banned operation of the narrow-body plane by Tuesday night.

“Boeing has a huge amount of money riding on this Max program,” said Robert Kokonis, president of airline consulting firm AirTrav Inc. “Today’s modern airline pilot needs vigorous training and flying experience, which means you’re able to respond to incidents more quickly and decisively.”

The global aviation sector has been expanding rapidly over the past decade, creating competition for experienced pilots and generating demand for fresh recruits, Mr. Kokonis said in an interview from Dubai, where he was speaking at an aviation finance conference.

“The reality is that aviation has been growing massively, especially in the Asia-Pacific, the Middle East and the Indian sub-continent,” he said. “There’s a shortage of pilots worldwide. Where do you get these pilots from? That’s not a good situation because these are complex airplanes with these new systems. But proper training and sufficient levels of flight-hour experience should be enough to fly the plane safely, provided there’s documentation and support from the manufacturer.”

Boeing said in a statement that it “continues to have full confidence in the safety of the 737 Max." The U.S. manufacturer added that, “out of an abundance of caution and in order to reassure the flying public of the aircraft’s safety," it recommended to the U.S. Federal Aviation Administration that Max aircraft be grounded worldwide.

“Safety is a core value at Boeing for as long as we have been building airplanes; and it always will be,” the company said. “We are doing everything we can to understand the cause of the accidents in partnership with the investigators, deploy safety enhancements and help ensure this does not happen again.”

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Fuelled by orders from Air Canada, WestJet Airlines Ltd. and other carriers, the 737 Max is the fastest-selling aircraft in Boeing’s history, with more than 5,000 orders from some 100 customers. Out of those total orders, more than 370 Max planes have already been delivered to airlines around the world.

So far, 41 Max 8s have been delivered to Canadian carriers: Air Canada (24), WestJet (13) and Sunwing Airlines Inc. (four).

Even before Canada grounded Max jets, other countries’ decision to ban the aircraft affected Canadian carriers. On Tuesday, for example, Air Canada confirmed the cancellation of its Halifax-to-London and St. John’s-to-London flights because of the British ban. WestJet said it has previously operated Max 8 planes on European flights from Halifax to Gatwick and Paris but that those seasonal routes are not in effect in the current schedule.

At Air Canada, the Max 8 has been replacing the Airbus A320. Canada’s largest airline has chosen the Airbus A220 jet, formerly known as the Bombardier C Series, to replace the Airbus A319 and Embraer 190 in the fleet.

No matter which aircraft they’re flying, pilots must be vigilant throughout a flight, and the takeoff is especially demanding, Mr. Kokonis said.

“The first phase of flight is very critical. You’re very busy with navigational issues. All these things are going on during a critical phase, and you’re preoccupied,” he said. “It goes back to training again. If things start to go wrong quickly, that’s when your long flight hours and experience as a commercial airline pilot and good training kick in.”