For the second time in about a month, United Airlines on Friday pushed back the date for its grounded Boeing 737 MAX aircraft to return to service.

The decision follows US aviation regulators' announcement this month they will not allow the aircraft to return to the skies this year.

The 737 MAX has been grounded worldwide for nine months following crashes in Indonesia and Ethiopia that left 346 people dead.

United Airlines now does not expect its MAX aircraft to fly again before June 4, three months later than the prior estimated date
United Airlines now does not expect its MAX aircraft to fly again before June 4, three months later than the prior estimated date GETTY / JUSTIN SULLIVAN

United now does not expect its MAX aircraft to fly again before June 4, three months later than the prior estimated date, resulting in the cancelation of more than 8,000 additional flights.

"We continue to automatically book affected customers on alternate flights," United said in a statement, adding that since the grounding the carrier had used "spare aircraft and other creative solutions" to lessen disruptions.

As the grounding of the MAX has dragged on, United, along with Southwest and American Airlines, have repeatedly delayed their expected date for the jets to fly again.

Boeing said earlier this month it will suspend production of the aircraft temporarily to focus on delivering the some 400 MAX planes it has since built.

United airlines