Airbus is examining a possible A321 fuselage modification which would aim to increase passenger capacity of the A321neo.
The modification would potentially take the A321neo to 235 seats.
Exit limitations mean the A321 is certificated, under European regulations, to transport a maximum of 220 passengers.
But Airbus executive vice-president for programmes Tom Williams says a higher-capacity version is "one of the things we're studying".
A321s have eight exits, four forward of the wing and four aft. The modification would involve adding another pair of doors, in the form of an overwing exit, and moving the position of the third pair.
The exit change could also require a new escape slide.
Williams says the A321neo "would be the target" for the proposed changes, which would allow a 235-seat configuration without a change in seat design.
Airbus has sought to increase seating on the A320 family by redesigning the galley area to use space more efficiently, but total seating has remained constrained by exit limits.
Williams would not indicate whether the study was being conducted for a specific customer.
But AirAsia chief Tony Fernandes, while confirming a new order for 64 A320neo and 36 regular A320s at Airbus's Broughton facility in the UK, said the carrier was looking at how to "get more seats into the aircraft".
The carrier's A320s are fitted with 180 seats, the maximum permissible.
AirAsia opted to stay with the A320 having considered a proposed high-density Bombardier CSeries.
As part of its new order AirAsia is taking options on 50 A321neos as well as 50 more A320neos.
AirAsia will take delivery of its latest 36 A320s up to 2016 - including 22 in 2015 alone - while its extra 64 A320neos will arrive over 2017-21.
It already had 200 A320neos on order which will be delivered during 2016-26. The carrier will make an engine decision on the latest order in January.