The US Federal Aviation Administration has found a new potential risk that Boeing must resolve on its 737 Max planes before the grounded jets can return to service, the agency says.
The risk was discovered during a simulator test last week – and appears likely to keep the planes grounded until December.
It is not yet clear if it can be fixed with a software upgrade or will require a more complex hardware fix, according to sources.
Boeing has been working to get its best-selling plane back in the air following a worldwide grounding in March in the wake of two deadly crashes within five months.
The company has been developing an upgrade for a stall-prevention system, known as MCAS, since a Lion Air crash in Indonesia in October, when pilots were believed to have lost a tug of war with software that repeatedly pushed the nose down.
A second deadly crash in March in Ethiopia also involved MCAS. In all, 346 people died the two air tragedies.
Reports of the latest issue comes as Boeing appears to be struggling with where to store all of its unsold Max 737s. The company is continuing to produce its flagship plane, but cannot sell them until the model is certified to fly again.
This week, Seattle news station KING-TV reported that a Boeing factory in Renton, Washington, was keeping the planes next to workers’ vehicles in the company car park.
Bloomberg estimates Boeing is storing 500 grounded 737 Max jets around the world, including 100 at the Renton factory.
The plane manufacturer has said the ground has already cost it $1 billion, with inventory costs predicted to reach $12 billion by September.
“We’re going to bring a Max back up in the air that will be one of the safest airplanes ever to fly,” Boeing CEO Dennis Muilenburg told Bloomberg.
“But we also know it will take time rebuilding the confidence of our customers and the flying public, and this will be a long-term effort.”
— The FAA (@FAANews) June 26, 2019
Sources said the latest issue with the Max planes meant Boeing would not conduct a certification test flight until at least July 8. The FAA will also spend at least two to three weeks reviewing the results before deciding whether to return the plane to service.
There had been hopes among airlines around the world that the 737 Max would be flying again in the northern hemisphere’s summer. That timetable was pushed back to late this year, even before the latest news.
Interviewed in Germany this week, the FAA’s associate administrator for aviation safety, Ali Bahrami, would not be drawn on a date for the planes to resume flying.
However, he told Bloomberg that comments by Mr Muilenburg projecting a return by the end of 2019 sounded correct.