The US Federal Aviation Administration said ​on Monday it will hold off certifying Boeing's long-delayed 737 MAX 10 until a newly-disclosed software issue is resolved, the latest ‌setback to the planemaker's efforts to bring the largest version of its best-selling jet to market, Reuters reported.

Boeing said on Saturday a software issue affecting certain 737 MAX aircraft could prevent pilots from accessing automated flight guidance during a specific landing scenario. The company said it had informed operators and was developing a software update to ​permanently address the problem.

Boeing shares closed down 6.9% over concerns about further delays to the MAX 10, a key aircraft in Boeing's ​effort to regain ground lost to Airbus in the lucrative single-aisle market.

"We will be delaying the 10 until ⁠we're satisfied that we don't have an issue here," FAA Administrator Bryan Bedford told reporters at an event at Reagan Washington National ​Airport. He declined to estimate the length of the delay.

The FAA said the software version can increase pilot workload when doing a go-around, ​where a pilot aborts a landing attempt, applies power, and climbs back into the sky to try to land again.

The FAA said earlier it planned to convene a Corrective Action Review Board to investigate the issue. However, the board is not likely to take place before next week at the earliest, two sources ​told Reuters.

The review by the U.S. regulator will test whether the software poses an unreasonable risk to safety, which could lead to more ​months of rework before the MAX 10 could get certified, which was widely expected to take place in October.

NOT A SAFETY CONCERN

However, WestJet, the Canadian carrier ‌backed by ⁠Onex Corp and one of the airlines operating the software on its 737 MAX fleet, said it had not experienced any in-service issues and did not view the matter as a safety concern.

"We have standard operating procedures and training to mitigate this type of event," the Calgary-based carrier said in a statement.

Three WestJet 737 MAX pilots, who spoke on condition of anonymity, said they were not aware of any issues with ​the software when performing missed ​approaches, a rare procedure.

Bedford said the ⁠software was supplied by jet engine maker and supplier GE Aerospace, and suggested a fix could be developed relatively quickly.

"I think in this particular case, due to the focus that's on it, GE may ​try to get this software correction in much quicker," Bedford said. "Is that weeks, days, months? I don't ​know."

Despite the bug, ⁠pilots maintained control, unlike undisclosed 737 MAX automatic flight control software that was involved in two crashes in 2018 and 2019, he said.

GE Aerospace did not immediately respond to a request for comment.

“We continue to follow the lead of the FAA as we work through the certification process," a ⁠Boeing spokesperson ​said.

Source: Reuters