Virgin America has become the first airline to order the re-engined A320neo, after committing to 30 of the type.
Chief executive David Cush disclosed the agreement today in Toulouse.
It covers 60 A320 aircraft in total, 30 of which are the A320neo.
"Virgin America will become the launch customer," says Airbus, although it says no engine selection has been made.
The US airline had tentatively agreed to take 60 A320s last year - a combination of 40 firm and 20 options - and indicated strong interest in a re-engined variant.
Virgin's order, booked in 2010, helped Airbus to leap from gross sales of 440 in November to 644 by the end of December.
Airbus also booked 56 aircraft from the Chinese state aircraft import company last month, as well as 10 A350-900s for Air China.
Virgin's deal, signed on 29 December, brought Airbus' overall orders to more than 10,000.