The Boeing 737 Max aircraft will not return to the skies before August, according to the head of aviation’s main trade body.

The 737 Max was grounded by regulators in the wake of two crashes, and although manufacturer Boeing has been working on a fix to allay safety concerns, it is likely to remain out of service for another 10 to 12 weeks, into peak season for many airlines.

Alexandre de Juniac, the chief executive of the International Air Transport Association, said the timing would depend on regulators, but he hoped to see a unified global timetable for the model’s reintroduction.

The grounding of the 737 Max came first in China and then Europe before the US Federal Aviation Administration (FAA) eventually followed suit, after a crash in Ethiopia in March that killed all 157 people on board. It was the 737 Max’s second disaster in five months, after 189 people were killed in Indonesia in October.

Speaking in Seoul ahead of the association’s annual meeting, De Juniac said airlines were not expecting a return to service within the next 10 to 12 weeks: “But it is not our hands. That is in the hands of regulators.”

Iata is planning a summit meeting between airlines, regulators and Boeing in July to discuss a coordinated timeline to restore the 737 Max to commercial flying, De Juniac said. “We hope that [the regulators] will align their timeframe,” he said.

The 737 Max disasters have ignited tensions between regulators on either side of the Atlantic, amid concerns over the FAA’s relationship with Boeing, including the degree of self-certification.

Ethiopia chose to send the data recorders from the crash to safety investigators in Paris, and the European Union Aviation Safety Agency has indicated it would carry out its own assessment of the 737 fix, rather than rely on the FAA.

According to Reuters, sources at ICAO, the UN aviation agency, believe the FAA will approve the 737 Max again as soon as late June.

US operators United Airlines, American Airlines and Southwest Airlines, early customers of the model sold as a more fuel-efficient iteration of the 737 shorthaul workhorse, have removed the planes from their flight schedules until early to mid-August.

De Juniac said prolonged grounding was “taking its toll” on airlines. Although Iata expects its 290 airline members to be recording a 10th consecutive year of aggregate profit, he said the 737 was adding to headwinds including “rising costs, trade wars and other uncertainties [that] are likely to have an impact on the bottom line”.

Figures for air freight releasedon Wednesday by Iata showed a 4.7% year-on-year decline in April. De Juniac added: “It is clear that trade tensions are taking their toll on the cargo industry.”