American Airlines is buying 50 of Airbus' newest long-range plane in a big boost for the just-launched A321XLR.

Airbus and the world's largest airline announced the deal Wednesday at the Paris Air Show, upgrading a previous order for A321neo jets to the A321XLR. No price tag was put on the contract but it is likely worth billions of dollars.

Airbus launched the A321XLR program Monday, a long-range version of its popular single-aisle A320 range, and has already signed several customers for the yet-to-be-built plane.

An Airbus A350 performs a demonstration flight at Paris Air Show, in Le Bourget, north east of Paris, France, Tuesday, June 18, 2019. The world's aviation elite are gathering at the Paris Air Show with safety concerns on many minds after two crashes of the popular Boeing 737 Max. (AP Photo Francois Mori)

An Airbus A350 performs a demonstration flight at Paris Air Show, in Le Bourget, north east of Paris, France, Tuesday, June 18, 2019. The world's aviation elite are gathering at the Paris Air Show with safety concerns on many minds after two crashes of the popular Boeing 737 Max. (AP Photo Francois Mori)

The move heightens pressure on Boeing, which is studying a new jet dubbed New Midsize Airplane, or NMA, that would be a similar size to the A321XLR. The American Airlines deal could give Boeing more incentive to push ahead with the NMA.

U.S. Air Force pilots based in England look on a Japan Kawasaki C-2 tactical military transport aircraft at Paris Air Show, in Le Bourget, north east of Paris, France, Tuesday, June 18, 2019. The world's aviation elite are gathering at the Paris Air Show with safety concerns on many minds after two crashes of the popular Boeing 737 Max. (AP Photo Francois Mori)

U.S. Air Force pilots based in England look on a Japan Kawasaki C-2 tactical military transport aircraft at Paris Air Show, in Le Bourget, north east of Paris, France, Tuesday, June 18, 2019. The world's aviation elite are gathering at the Paris Air Show with safety concerns on many minds after two crashes of the popular Boeing 737 Max. (AP Photo Francois Mori)