Airbus SE is falling behind on deliveries of the A321XLR, a longer-range version of its most popular jet, with Indian customer IndiGo unlikely to receive the full batch of nine units this year, according to people familiar with the matter.

InterGlobe Aviation Ltd., the operator of Asia’s largest low-cost carrier, was supposed to receive the XLRs by year’s end, but the time frame on some units has been pushed back by several months, said the people, asking not to be identified because the information isn’t public. IndiGo has received two XLR jets so far, and they’re being used on routes to Athens and Istanbul. 

The airline was told the Middle East war is disrupting the planemaker’s supply chain, the people said. IndiGo is now negotiating with the France-based manufacturer for favorable delivery slots, the people said.

An Airbus spokesperson said the company doesn’t comment on delivery schedules agreed upon with customers. IndiGo said there’s currently no change in the delivery timeline, and the airline will receive its third XLR in a few days.

The XLR, which stands for “extra-long range,” is meant to open long-haul routes for budget airlines that fly single-aisle aircraft rather than the more complex widebody models. IndiGo placed an order for 40 of the new aircraft.

The XLR delays would represent another hurdle for IndiGo’s ambitious international expansion, which is under pressure from soaring jet-fuel costs and airspace restrictions. The carrier reported an unexpected loss in the first quarter and said this week it was suspending flights to Hong Kong and Shanghai until at least October.

Airbus began delivering the XLR to customers last year. The plane combines the economics of a narrowbody aircraft with the range of a longer-range model such as the bigger A330.

At the same time, flying long routes with a single-aisle airframe comes with operational complexities, making the aircraft more of a niche choice than the popular A321.