The world’s aviation regulators have yet to agree on a unified approach to recertifying the Boeing 737 MAX, which was grounded after two fatal crashes that killed more than 300 people, the head of the International Air Transport Association said Tuesday.

Alexandre de Juniac told Bloomberg TV in Berlin that lack of unified approach threatens to undermine the flying public’s trust.

“The point on which we have to pay attention is for the regulators to be aligned,” de Juniac said. “Otherwise the certification process will be broken, will be fragmented, and we have built our safety record on the unanimity and reciprocity of the certification process.”

The 737 Max was grounded in March following the second crash within five months blamed on faulty sensors in the plane’s automatic system for maintaining the plane’s pitch. Planes operated by Lion Air and Ethiopian Airlines crashed, killing 346 people, after the system kept pushing the nose down and pilots were unable to compensate.

Boeing said last week it is working closely with the U.S. Federal Aviation Administration and other regulatory agencies to get the plane back in the air, shooting for recertification in December and a resumption of commercial passenger flights in January.

The fixes include updated pilot training, which is scheduled to begin in January.

Automation is an integral part of making planes more efficient and safer, but pilots worry the advanced electronics are degrading their flying skills.

Bo Corby, director of standards and training for Future & Active Pilot Advisors, told USA Today pilot training at many airlines is focused on using automated systems to the detriment of flying skills.

United, Southwest and American airlines all have removed the plane from their schedules through early March even if the plane is ungrounded before then. Southwest has 34 of the planes; American, 24, and United, 14.

Boeing said once the plane is ruled airworthy, it will resume making deliveries. The company announced orders for 50 jets worth $6 billion at the Dubai Airshow Monday.