ATR is continuing to work on the definition of a 90-seat turboprop which could see entry into service by around 2017.
Speaking at the airframer's annual results briefing in Paris on 18 January, chief executive Filippo Bagnato said that it was targeting the end of the year for a decision from its shareholders, EADS and Alenia Aermacchi, on whether to launch the programme.
"The definition is vital: without a clear understanding of the major systems, it is just an empty cabin," he said.
"We have an idea of what it will look like and the various options for the engine."
The aircraft would be larger than the current ATR 72-600, he said, with a longer fuselage and the possibility of stowing luggage under the floor.
ATR has already entered discussions with incumbent engine provider Pratt & Whitney Canada and rival GE over possible powerplant options for the 90-seater, said Bagnato.
However, he ruled out any involvement from Rolls-Royce at this stage.
"What we have said to GE and Pratt is that we don't want any surprises - we don't want to reinvent the wheel.
"ATR's dimensions are such that we can't imagine the risk of developing a [completely] new type of engine," he said.
A number of new components - including the turbine and combustion chamber - are in development by P&WC's sister company Pratt & Whitney for its PW1000G geared turbofan, itself sharing a common core with the 1,000lb-thrust-rated PW800. These, and a separately-designed compressor, are likely to find their way onto any new P&WC turboprop, said Bagnato.
The current generation of ATR 42-600 and 72-600 are powered by the Pratt & Whitney Canada PW127 engine.
ATR forecasts a market over the next 20 years for around 3,100 regional turboprops: 500 in the 50-seat range, 1,000 90-seaters and 1,600 with 70 seats.
Head of sales John Moore said customers are increasingly expressing interest in a higher-capacity turboprop. He said: "They can see a real need for a bigger aircraft. We are getting some pressure from them but that helps us promote the case to our shareholders."
However, Bagnato said that it will not neglect its core market. "We have to be competitive over the next 20 years with the 50- and 70-seaters," he said.
Any technological advancements introduced on a 90-seat aircraft would flow down to the smaller variants, he added.
Bagnato anticipates it would take around four years of development to bring a 90-seat aircraft to market.
Rival Bombardier has previously indicated it is looking at developing a larger version of its 70-seat Dash 8 Q400 for entry into service in the second half of the decade.
Chris Seymour, head of market analysis with Flightglobal's Ascend consultancy business, said a 90-seat aircraft with "more efficient engines" would be the "next logical step".
"A highly efficient, high-capacity aircraft for short-haul routes should be a very attractive prospect," he said.