MONTREAL -- Canada's two biggest airlines pushed back the return of the beleaguered 737 Max after airplane maker Boeing Co. said it did not expect regulators to green-light the jet for takeoff until the middle of the year.

The delay until late June by Air Canada and WestJet Airlines Ltd. follows similar moves by American Airlines, United Airlines and Southwest Airlines, further jeopardizing routes and profit margins.

The U.S. Federal Aviation Administration and Boeing have continued to find defects with the aircraft that fall outside of the automated software system known as MCAS.

Ottawa banned the 737 Max from the skies last March following two fatal crashes in five months that MCAS contributed to and that saw the plane grounded worldwide.

The airlines' decision marks the latest in a series of delays that have hampered growth plans, reduced revenue and capacity and bumped up costs for the carriers, which have had to spend more on leases for aircraft that are less fuel-efficient.

Air Canada had been on track to have 36 Max 8s -- one-quarter of its narrow-body fleet -- by the end of 2019, with 14 more scheduled to arrive this year. WestJet was slated to receive two last year and two in 2020 on top of the 13 now sitting idle.

Air Canada said Wednesday that scrubbing the Max from its schedule for the second time in three weeks was based on operational considerations and meant to provide customers with certainty around planning and booking travel.

Earlier this month the Montreal-based airline opted to push back the return of the aircraft until March 31, with the new re-entry date pegged at June 30.

WestJet announced Tuesday that it will remove the plane from its flight schedule until June 24.

"We thank our guests for their patience and our WestJetters for their commitment to keeping our airline moving safely and on time as we continue to adjust our schedule," said WestJet chief executive Ed Sims in a statement.

Despite thousands of cancelled flights, both airlines have completed the vast majority of their planned departures during the now 10-month grounding.

"Returning the Max safely to service is our No. 1 priority, and we are confident that will happen," Boeing said in a statement Tuesday.

"We acknowledge and regret the continued difficulties that the grounding of the 737 Max has presented to our customers, our regulators, our suppliers and the flying public."

This report by The Canadian Press was first published Jan. 22, 2020.