United Airlines’ Tuesday announcement of an order for 50 Airbus A321XLRs to replace its fleet of aging Boeing 757s might have struck another serious blow to the business case for Boeing’s proposed twin-aisle NMA, a project about which the U.S. company has said little since the second crash and subsequent worldwide grounding of the 737 Max. In fact, not long after Boeing CEO Dennis Muilenburg told investment analysts during the company’s third-quarter earnings call that the NMA remains a subject of study, Boeing Commercial Airplanes vice president of marketing Randy Tinseth responded to a question about the status of the NMA at a Dubai Airshow press conference with a reference to how the company’s priorities reside with the Max.

United, meanwhile, had already reached the late stages of negotiations on the A321XLR, an airplane it calls an “ideal one for one replacement” for its older, less fuel-efficient jets—namely, its 757s.

Although United hasn’t completely ruled out an NMA order if and when Boeing offers it, the XLR deal will certainly lend support to Airbus’s argument that its airplane can serve many, if not most, of the markets Boeing’s product would target. For its part, Boeing pointed to its own commercial successes with United. “We are proud of our decades-long partnership with United Airlines, and our team is focused on delivering on outstanding orders for nearly 200 new airplanes for United in the coming years,” it said in a statement. “We look forward to continuing to support United’s future fleet and operational requirements.”

United expects to take its first A321XLR in 2024 and start flying between Europe and North America with the new narrowbodies the following year, not long before the time Boeing originally had targeted for service entry of the NMA. With the order, United becomes the second airline to choose the longest-range version of the A320neo family. Over the summer American Airlines placed a new order for 20 XLRs and converted delivery positions on 30 A321neos to the new jet.

Launched during June’s Paris Airshow, the A321XLR will fly as far as 4,700 nm, or 700 nm farther than the A321LR. Changes in the XLR include a permanent rear center fuel tank as opposed to the auxiliary fuel tanks in the LR, modified landing gear to account for an increase in mtow to 101 tonnes from 97 tonnes, and an “optimized” wing trailing-edge flap configuration to preserve the takeoff performance and engine thrust requirements of today’s A321neo.