Lessor CIT's firming of orders for another 10 Airbus A330s gives the airframer its first commitment to the higher-weight variant unveiled earlier at the show.
But CIT has yet to detail how many of the twinjets will be built as the new weight variant - and whether these would be the -200 or -300 model.
CIT has firmed a previous agreement for five A330s and is taking an additional five under the deal disclosed at the Farnborough air show. It has not given an engine selection.
But deliveries of the 10 A330s will begin in 2014, a year before the higher-weight 240t variant is produced, which means some of the aircraft will not be the new version.
CIT Transportation Finance chief Jeffrey Knittel did not give a precise order breakdown, but said the lessor had "flexibility" and the eventual production would be "based on what airlines require".
But he indicates a market leaning - particularly in Asia - towards the -300 rather than the -200.
Knittel would not say how many higher-weight aircraft would be in the fleet, but stresses that the original 212t A330-300 was a "limited range" aircraft, and that subsequent increases in weight have created a jet capable operating both as a short-range and long-range transport.
He adds that the new A330 version "complements the A350", for which the lessor has an order for five. CIT had originally ordered the A350-800 but converted up to the larger -900 last year.