Canadian airframer Bombardier expects to finalise within the next few weeks the tentative agreement with local operator WestJet for up to 45 Q400 turboprops.
The Canadian airframer's vice-president of marketing, Philippe Poutissou, insists that, while the customer was on its own turf, the order was "by no means a given".
Calgary-based WestJet will use the Q400s to form a new regional carrier in the second half of 2013, although its initial routes will be disclosed this year.
WestJet had been weighing the Q400 against the rival ATR 72-600, and Poutissou says Bombardier was "well aware that WestJet was quite diligent in evaluating the competition".
The airframer has not disclosed a value for the potential order, comprising 20 firm and 25 optioned aircraft.
Once concluded the WestJet agreement will lift a flagging Q400 backlog which had dipped to 24 aircraft by the end of last year - just a few months' production - and will bring overall sales for the type to 428. Bombardier has secured orders for 15 Q400s this year from Ethiopian Airlines, EuroLOT and Horizon Air.
WestJet states that it selected the Q400 for its range and speed - the type has a claimed range of over 1,000nm with 74 passengers against 830nm for the ATR with 70.
Poutissou says the Q400 is "well-adapted to the Canadian environment and climate" and adds that he believes the manufacturer "had the right product" for WestJet.
While ATR has a large order backlog, Poutissou says ATR is "very creative" and could have met the tight delivery schedule - although he states that delivery positions, while important, are not the "dominant" factor in aircraft selection.
He says that Bombardier put a "lot of pressure" on itself to secure the WestJet deal and stresses that, while the carrier is Canadian, the agreement was not simply a shoo-in for Bombardier. "WestJet is publicly-traded and answers to its shareholders," he states.
Bombardier expects finalisation of the WestJet agreement to "take a few days, possibly weeks". It has yet to fix a delivery date.