[NEW YORK] Boeing on Tuesday officially pushed back the timeframe for the 737 MAX to return to the skies, sending shares plunging and overshadowing an earlier announcement of a first flight of the delayed 777X plane.

Boeing said it is now targeting the return of the grounded MAX "during mid-2020," the latest delay in the schedule for the troubled jet, which has been grounded since March following two deadly crashes.

Boeing shares were down nearly five per cent in afternoon action at US$308.59 after the New York Stock Exchange halted trading for around 40 minutes.

The company is in the process of raising at least US$10 billion from Wall Street banks to cover costs connected to the MAX crisis, bank sources said Monday.

Boeing has told customers and suppliers "that we are currently estimating that the ungrounding of the 737 MAX will begin during mid-2020," the company said in a statement.

The statement is a shift from Boeing's most recent stance on the status of its top-selling aircraft, that eliminated a target date entirely after timeframes repeatedly mapped out in 2019 were not met.

But even the vague mid-2020 target is later than some analysts had expected, and though it probably represents a best-case scenario and could again be pushed back.

The Federal Aviation Administration had publicly criticised Boeing for continually touting its aggressive timeframe in public for the MAX's return, suggesting the target was a tool for pressuring the agency into approving the plane more quickly.

On Tuesday, an FAA spokesman reiterated that it has set "no timeframe" for the MAX's certification.

"We continue to work with other safety regulators to review Boeing's work as the company conducts the required safety assessments and addresses all issues that arise during testing," the FAA said.

The MAX statement overshadowed an earlier announcement that the 777X would undertake its first flight on Thursday, progress for a key widebody jet that has itself been delayed for different reasons.

AFP