Lufthansa is choosing between Boeing’s B737 Max and Airbus’s A320 neo to replace more than 100 aircraft in its fleet, according to its CEO.

“We have not lost our trust in Boeing” Carsten Spohr said Tuesday, according to Reuters.

Seattle-based Boeing has faced weeks of speculation over whether two recent plane crashes, both involving a B737 Max 8, were caused by an issue with an automated system designed to prevent the aircraft from stalling, known as MCAS.

“They’ve built wonderful aircraft over the decades, and I am sure they will fix the current issue,” Spohr continued.

“Between Boeing and the [US Federal Aviation Administration], I think this country will not rest until you have gone to the ground of what really happened there and is there something to improve.”

Lufthansa’s decision will not be made until next year. Its current fleet comprises mainly Airbus aircraft, and it has almost 150 A320/A321 neo aircraft on order, with some already in service. The new aircraft will replace its Airbus A319 and Bombardier CRJ planes.

The single-aisle B737 Max and A320 neo are both recent evolutions of best-selling models from rivals Boeing and Airbus, with Boeing developing the model to compete with the latter’s fuel efficiency and other selling points.

The B737 Max was grounded by regulators around the world as a precautionary measure until further information about the cause of the crashes comes to light. American Airlines said it will be cancelling 90 flights per day until at least April 24 as it awaits an update from the US Federal Aviation Administration.

Last week Indonesia’s flag carrier Garuda cancelled its US$6 billion order for 49 of the aircraft, stating that “passengers in Indonesia have lost trust and no longer have the confidence [in the aircraft]”. The first B737 Max 8 crash, in October 2018, was operated by Indonesian low-cost airline Lion Air.

The CEO of Ethiopian Airlines, which saw the second crash on March 10, said earlier this week that the carrier “believes in Boeing,” and that the companies will “continue to be linked well into the future.”