(Reuters) -Boeing ( BA ) is in the early stages of developing a new single-aisle airplane that would eventually replace the 737 MAX, the Wall Street Journal reported on Monday, citing people familiar with the matter.

Earlier this year, CEO Kelly Ortberg met with officials from Rolls-Royce Holdings in the UK to discuss a new engine for the aircraft, according to the WSJ report.

The U.S. planemaker has also been designing the flight deck of a new narrow-body aircraft, the report said, adding that development remains in the early planning phase, with final decisions yet to be made.

Reuters could not immediately confirm the report. Boeing ( BA ) and Rolls-Royce did not immediately respond to a Reuters' request for comment.

The 737 MAX entered service in 2017, but the model was grounded globally in 2019 following two fatal crashes.