Boeing shares rallied Thursday following a top US air safety regulator that a certification flight for the 737 MAX could occur within weeks.
Boeing also confirmed that it encountered a fresh issue with flight software on the plane, but said it does not expect the problem to further delay the aircraft's return to service.
Federal Aviation Administration chief Steve Dickson told reporters in London that a MAX certification flight could occur in "a few weeks."
Dickson said he met with officials at Britain's Civil Aviation Authority on Thursday as part of an effort to align global regulators, but said there still was "no timescale" for returning the jet to service.
The MAX has been grounded since March 2019 following two crashes that claimed 346 lives.
After repeatedly missing its goals for resuming flights last year, Boeing is targeting a mid-2020 return, but says the timeframe will depend on regulators.
The latest issue on the MAX occurred during a flight test when an indicator light associated with a flight handling system illuminated when it should not have, a Boeing spokesman said.
Boeing notified the FAA of the issue the week of January 20 and has also told airlines.
"Our current schedule assessment indicates that this change will not impact the present mid-2020 estimate for return to service," the Boeing spokesman said.
Boeing shares jumped 3.7 percent to $341.73 in midday trading.