Doerksen points out that at the time of its first flight, the Embraer 170 had only 112 firm orders and fewer customers than the CSeries, and orders picked up later. “We expect a similar situation for Bombardier, with first flight likely to be the major catalyst for airlines to pull the trigger on ordering aircraft,” he says.

But Bombardier's commercial aircraft business relies heavily on the success of the CSeries. In its most recent market forecast update, the company projects deliveries of 12,800 aircraft in the 20-149-seat range in 2012-13, with the CSeries size category accounting for 71% of that market in terms of revenues.

Whether that forecast will become reality also depends on a relaxation of scope clauses that limit the use of larger aircraft by the regional subsidiaries of mainline carriers. Mairead Lavery, vice president of strategy, business development and structured finance at Bombardier, sees some movement in the U.S. as negotiations on scope clauses are underway at several airlines. But this is far from an industry trend. There has been some relaxation of limits in Europe and more could come as the International Airlines Group, Air France-KLM and Lufthansa Group dig further into the details of their respective cost-savings programs. But scope clauses have not been at the top of their most recent agendas.