Airbus is looking for firmer details on Boeing's proposal to address the middle-of-the-market sector before committing to possible further enhancements on the A321neo.
Its A320 programme chief, Klaus Roewe, hints that a further stretch is "not out of reach" but cautions that the A321neo is nearing the limits of improvement short of extensive redesign.
The European airframer has been promoting the A321neo – currently designed for up to 240 passengers – as a fit for the sector between single-aisle and twin-aisle operations.
Boeing has been working on a proposal designated the New Mid-market Airplane, but the company has yet to release details on the potential design.
Speaking to FlightGlobal during the first flight of the latest A321neo variant, the A321LR, Roewe said the manufacturer was waiting to see what its rival might offer.
"We know we're in a good position," he says. "But it's never so good that you have to do nothing at all."
He says the A321LR is "in the sweet spot" and describes it as the "perfect answer" to the Boeing 737 Max 10, claiming that the US airframer has "sacrificed performance".
The A321neo has evolved into a popular variant, accounting for 32% of all orders for the re-engined A320neo family, compared with 22% for the A321's proportion of previous regular A320 orders.
Airbus figures show that A321neo orders comprise 1,920 aircraft and exceed total orders for the A321, which first flew 25 years ago.
"We never give up on improving, and looking for further opportunities," says Roewe, stating that the airframer is looking at taking the A321neo's capacity to 244 seats "and potentially beyond".
But he admits the A321neo is close to limits for enhancement. A stretch would probably require both fore and aft plugs to avoid centre-of-gravity disturbance, but stretching the aft fuselage presents additional tail-strike risks and would need careful analysis of speed-management and performance.
A larger aircraft could mean exceeding the capability of the A321neo's engines, risking loss of commonality and higher maintenance costs. Roewe points out that the A321LR, which will have a maximum take-off weight of 97t, did not need a new thrust rating for its powerplants.
He adds that there is also a deterrent to increasing the seating capacity. While Roewe indicates that A321neo exit limits with its revised door configuration could potentially offer a 250-seat aircraft, the legal requirement to add further cabin crew means that pressing for higher accommodation "doesn't make economic sense".
Roewe says, however, that Airbus is under "no pressure" to make any significant developments, and says that it does not need – for now – to engage in any "further provocation" of Boeing.