(Reuters) -The first delivery of Airbus' longest-range narrowbody jet, the A321XLR, is poised to slip into October, apparently missing the planemaker's delivery target by several weeks.

A spokesperson for Spain's Iberia said in response to a Reuters query that the delivery is planned for the second half of October.

Airbus referred questions on the delivery to the airline. In July, it said it expected the A321XLR to be delivered "at the end of the summer," having previously cited the third quarter.

The delivery from Hamburg represents a milestone in a fierce competition between Airbus and Boeing to meet demand to serve longer routes with workhorse narrowbody jets.

The A321XLR was launched in 2019 with an initial target for entry to service of 2023 to help airlines open new routes without the need to fill up larger wide-body aircraft. Boeing is developing a larger version of its 737 family, the MAX 10.

The debut A321XLR delivery was originally earmarked for Iberia's sister airline Aer Lingus but was switched to the Spanish network by parent group IAG earlier this year amid uncertainty during a recent Aer Lingus pilots' strike.

The uncertainty spilled into the paint shops with one aircraft seen recently in Aer Lingus colours but with an Iberia logo on the engine cover during testing, according to industry publication the Irish Air Letter, which expects Aer Lingus to receive two of the long-distance planes in the fourth quarter.

Airbus said it had sold more than 500 of the recently certified A321XLR model but did not give a breakdown by airline.

IAG did not immediately respond to a request for comment.