US aircraft manufacturer Boeing has said a cut in jet production after two deadly crashes involving its planes has already cost it $1bn (€900m).

The company said its profits fell by more than a fifth in the first quarter of this year.

Its fleet of 737 MAX airliners remains grounded worldwide after separate crashes in Indonesia and Ethiopia killed 346 people.

This evening, the company said it was too early to calculate the overall impact on its financial results for the year.

The manufacturer has now suspended its earnings forecasts.

737 Max

Executives at the company said they cannot say for sure when the grounding of the 737 MAX is likely to end or when it can resume delivering the planes.

Chief Financial Officer Greg Smith said: "We will continue to apply whatever resources are required to return the 737 Max safely into the fleet and take the time necessary to do so."

Air accident investigations have determined that the pilots of both planes encountered difficulty overcoming a safety feature that forced the nose of the aircraft down before the crashes.

Boeing

Boeing said it has since performed more than 135 test flights using new software as part of a process to get the fix certified by aviation authorities.

"Across the company, we are focused on safety, returning the 737 Max to service, and earning and re-earning the trust and confidence of customers, regulators and the flying public," the company’s CEO Dennis Muilenburg said in a statement.

He said he has personally flown on two of the test flights.