European pilots stepped up pressure on the region’s air safety agency to take a strong stance in vetting U.S. plans to return Boeing Co.’s grounded 737 Max to service after two fatal crashes.

The European Aviation Safety Agency needs to take steps to regain the confidence of air crew, according to the head of the pilot lobby, who also urged more training on revisions to the Max before it returns to the skies.

“We really would like some serious action and transparency to show how they are going to certify the return to service of this aircraft,” European Cockpit Association President Jon Horne said in an interview. “It’s critical to regaining credibility among our community.”

The ECA, which represents pilots at Max operators including Ryanair Holdings Plc and Norwegian Air Shuttle ASA, is unhappy with the expanding role of planemakers in licensing new models. Boeing had an important hand in certifying the original Max design and the European regulator signed off on it.

A lack of funding has forced the measure on regulators such as the U.S. Federal Aviation Administration, which had ultimate authority for the Max, but has created a conflict of interest, Horne said.

Simulators

A return to service for the Max after two crashes in five months must come with new simulator training for pilots, including experience handling the aircraft without the so-called MCAS anti-stall function blamed for the tragedies, Horne said. The ECA is also concerned that “Boeing is still talking about minimizing the training in any fix-package,” he said, adding that a return may need to be delayed until enough flight-simulators can be rolled out to airlines.

The European Parliament’s transport committee last month asked EASA to explain how it will assess the airworthiness of a revised Max, urging the body to defend its watchdog status after the FAA’s “failed” oversight of Boeing. EASA has already said that it will undertake its own review. It didn’t immediately respond to messages seeking further comment.

The European aviation industry has “some identical dynamics” to the FAA-Boeing relationship that present “similar vulnerabilities in Europe’s certification process,” Horne said, adding that the pilot community wants to see more transparency in EASA’s dealings with manufacturers.

The ECA’s concerns aren’t limited to the 737, with the lobby group calling for a review of Boeing’s new 777X, which like the Max is a re-engined version of an earlier model, but also features new wings. Regulators must be clear that the U.S. company isn’t making compromises to deliver on promised performance gains, Horne said.