Air Canada has extended the absence of the 737 Max from its schedules through 30 June as the grounding of the aircraft drags on and the US Federal Aviation Administration continues its review of whether they are safe to resume service.

The Montreal-based carrier’s 22 January announcement comes a day after Boeing stated: “We are currently estimating that the un-grounding of the 737 Max will begin during mid-2020.” That prediction was based on the progress of the certification process.

Cirium fleets data shows that Air Canada has 24 Max 8 in storage and another 26 on order, along with 11 Max 9s.

Boeing had prior to December estimated that regulators would clear Max jet to fly by the end of 2019. That was before FAA administrator Steve Dickson said too much work remained on the certification process. The FAA has shied from providing a timeline, but industry observers had speculated that certification would come early in 2020, perhaps before April.

Air Canada’s decision reflects growing uncertainty among airlines. On 21 January, shortly after the Boeing announcement, Canada’s second-largest carrier WestJet took the Max out of its schedule until 24 June. WestJet has 13 Max jets in storage and 44 on order, according to Cirium fleets data.

Airlines have worked hard to adapt during the grounding while cancelling a minimum of flights, but it is uncertain how long they can continue emergency measures that include extra hours for their maintenance staff to maximise the service availability of other aircraft. Extending the Max’s absence for a second summer travel season would also deepen the potential hit to profits from diminished capacity.

Air Canada extended aircraft leases to offset the impact of its grounded Max aircraft, which account for 24% of its narrowbody fleet. The Star Alliance carrier’s third-quarter profit declined 9% to C$636 million ($487 million).