This new Airbus jet is bad news for Boeing

Airbus has a new jet that's winning over some of Boeing's best customers.

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It also raises the specter of more trouble ahead for the U.S. plane maker.

The European company started delivering the new aircraft the A321XLR-late last year against a backdrop of manufacturing upheaval and financial strain at its American rival. So far the XLR has racked up more than 500 orders, many from airlines looking to replace older Boeing planes.

The jet's success is one of the starkest signs yet of the diverging fortunes of the two companies, with Boeing's troubles leading to gaps in its product lineup that are now being exploited by Airbus. It is also a warning of a bigger threat looming: While Boeing is strapped for cash, Airbus is increasingly investing in an entirely new generation of aircraft that could shape the duopoly for decades to come.

American Airlines and United Airlines have chosen Airbus's XLR to replace their aging Boeing 757 fleets. Other airlines including Australia's Qantas have also purchased the XLR-the first time that carrier has ordered one of Airbus's smaller, narrow-body jets.

Central to the XLR's appeal is a giant fuel tank behind the wings that means the aircraft can carry up to 220 passengers on trips as long as 11 hours.

That is far longer than typical narrow-body jets, allowing airlines to open up new direct routes including across the Atlantic without needing to sell as many tickets as they would with a bigger, wide-body plane.

The new model-the latest in its A320 family of aircrafthas another advantage: It doesn't have much competition. Boeing discontinued the 757 in 2004 and shelved plans to build a new aircraft that would have competed directly with the XLR in 2020. The U.S.company's main rival aircraft the 737 MAX 10-is years behind schedule, awaiting signoff from the Federal Aviation Administration.