Airbus appears to be dismissing the possibility of a further stretch to the A350, despite the capacity gap between the A350-1000 and the A380.
The A350-1000 will be capable of seating 350 passengers in a typical three-class configuration, according to the airframer. High-density arrangements could lift this to 440.
Its A380 has a 525-seat layout, although some carriers have fitted low-density layouts of just over 400 seats.
While Airbus positioned the A350-900 as the central platform for the three-member family, the backlog of the smaller A350-800 is eroding in favour of the larger variants.
But the airframer does not see room for a further stretch beyond the A350-1000.
"A double stretch has never been shown to work in this industry," claimed Airbus chief operating officer for customers John Leahy, speaking in Toulouse on 16 January.
"We couldn't do it. And we don't think [Boeing] could do it either."
The A350-1000 underwent a redesign in 2009 to improve its thrust and range capabilities but Airbus resisted stretching the fuselage. The -1000 has yet to achieve convincing sales - a matter Leahy attributes to slot availability - but the aircraft has attracted orders from Cathay Pacific and Qatar Airways.
Boeing has been considering stretching the 777-300ER, under its 777X project, to modernise the twinjet and compete against the A350-1000.