Four of the world’s leading aircraft regulators have agreed in principle to coordinate in restoring Boeing Co.’s (BA.N) 737 Max to service once they’re confident that technical updates and new training meet safety standards.

The tentative pact is an attempt to avoid the fractious approach taken in grounding the jet after two deadly crashes, people familiar with the discussions said. Officials from the U.S. Federal Aviation Administration have had discussions with their counterparts in Europe, Canada and Brazil and came away believing there is consensus on the need to act together to restore public trust in the world’s aviation-safety system.

The rising sense of cooperation suggests that other leading regulatory agencies are gaining confidence in the U.S. process for assessing Boeing’s fix. A renewed convergence would mark a reversal from what airlines and even Boeing’s top rival have feared -- a disorderly approach to recertifying the Max that would further strain ties between the FAA and European Union Aviation Safety Agency, the global standard-bearers for safety.

“We’ve been working, all of us in the industry across borders, to some degree, to get the rest of the regulators in all the other countries to return that aircraft to flight at roughly the same time,” Oscar Munoz, Chief Executive Officer of United Airlines, said this week at the Aspen Ideas Festival. “It’s not going to look good if one brings it up and no one else does.”

The FAA’s associate administrator for aviation safety, Ali Bahrami, met earlier this month in Europe with his counterparts at other agencies, according to a person familiar with the discussions. The FAA believes that the other countries are ready to act closely with the U.S. to lift the grounding, said the person, who wasn’t authorized to discuss the talks and asked not to be identified.

Volatile Politics

The volatile politics swirling around the Boeing jet -- which includes multiple investigations and calls by some U.S. lawmakers and foreign leaders for significant changes to the plane -- mean that there is still no guarantee that there will be collaboration, the person said. Another wildcard is China, a crucial market for Boeing, and the first country that grounded the Max.

This week’s revelation that FAA test pilots had found a new risk factor in the plane and were ordering the manufacturer to revise a flight computer highlights how fluid the situation remains. Boeing’s timeline for completing the Max software fixes has repeatedly slipped while regulators have expanded their review to include a cockpit alert that wasn’t widely operational and an extensive look at pilot training.

But the company has been telling customers and others with a stake in the 737 Max’s future that it anticipates it can address the issue as well as a broader software redesign, and return the plane to service in a September time frame, said people familiar with the manufacturer’s talking points.

The 737 Max family of aircraft was grounded on March 13, after the second fatal crash within five months was linked to malfunctioning flight-control software. Boeing is still working with FAA engineers to fine-tune a software redesign for the plane and establish what types of new training will be needed for pilots before flights can resume.

In the days after the March 10 crash of an Ethiopian Airlines 737 Max 8 near Addis Ababa that killed 157 people, the world’s aviation regulators fractured. Numerous regulators, including China and EASA, grounded the plane before the FAA acted. The FAA said it didn’t make a decision until it had received hard data indicating the two crashes were linked.

That disparate response runs counter to decades of attempts to standardize the process of certifying aircraft and setting safety standards. The effort is designed in part to make it easier for manufacturers to get new planes to market, but also to help reduce the accident rate by agreeing on common standards.

Global regulators are trying to restore more collaboration. Another person briefed on talks involving the different regulatory agencies said that while EASA and other nations may not return the Max to flight at the same time as the FAA does, they are likely to follow within days of U.S. action.

The four regulation agencies -- which collectively oversee Boeing, Airbus SE, Bombardier Inc. and Embraer SA -- formed a task force after the grounding because they felt it would cause problems with the world’s aviation system if the FAA acted alone to return the plane while others sat on the sidelines, said a person familiar with the the workings of Brazil’s National Civil Aviation Agency.

“We’re seeing a convergence amongst the regulators,” Boeing CEO Dennis Muilenburg said June 16, noting that FAA officials are working closely with counterparts in Europe, Brazil and Canada. “There’s certainly an advantage to bringing the airplane back up around the world in a highly synchronized fashion.”

Once the grounding is lifted, the first of the planes could be airborne within weeks, although it will likely take months before the more than 500 Max in storage enter the global fleet, Muilenburg said this week. That total includes as many as 150 newly built jets that haven’t been delivered.

Any decision to return the Max to the skies will also depend on Boeing’s effort to eliminate risks created by the Maneuvering Characteristics Augmentation System, which has been implicated in the two accidents, the people said. An MCAS malfunction can repeatedly command a plane to dive.

The FAA has briefed some airline industry officials on its efforts to work closely with Europe, Canada and Brazil, another person familiar with the discussions said. The U.S. regulator has said repeatedly that it doesn’t have a time line for restoring the plane to service.

Just two weeks ago, Patrick Ky, executive director of EASA, said the agency was considering whether Boeing should have to add an additional sensor to the plane, which would boost the cost and complication of recertifying the plane.

However, some powerful voices in international aviation have been calling on EASA and other agencies to work more closely with FAA.

Airbus CEO Guillaume Faury has said several times, including last week at the Paris air show, that he’s concerned about tensions between different aviation regulators in the wake of the 737 Max crashes. It’s important that there be “one system,” Faury said.

Airlines’ View

The International Air Transport Association, which represents carriers around the world, urged regulators in a press release on Thursday “align on technical validation requirements and timelines for the safe re-entry into service of the Boeing 737 MAX aircraft.”

“We trust the Federal Aviation Administration, in its role as the certifying regulator, to ensure the aircraft’s safe return to service,” said Alexandre de Juniac, the group’s director general.

The FAA has been “transparent and collaborative” with other nations’ regulators as it assesses the 737 Max issues, the agency said in a statement.

“As to the aircraft’s global return to service, each government will make its own decision based on a thorough safety assessment,” the agency said.

While FAA Administrator Daniel Elwell has said that the agency is taking the lead on evaluating the plane’s safety because it is made in the U.S., he has also signaled that he would welcome other nations taking a similar approach.

“We want every country who has been part of this to be reading from the same book that we have written on the Max and are continuing to write so that, such time when we’re ready to lift that prohibition, there is absolutely no question in any other country’s mind why we’re doing it and how we got there,” Elwell said last month as the agency prepared to host regulators from other countries at a meeting in Texas.

--With assistance from Mario Sergio Lima, Mary Schlangenstein, Justin Bachman and Richard Weiss.