MIAMI — Bombardier has removed from the CSeries production schedule a six-year-old order placed by Republic Airways, although it will remain in the program backlog.

Back in 2010, Republic placed the largest CSeries order to date for 40 CS300s. These aircraft were going to fuel the expansion of Frontier Airlines after its merger into Midwest Airlines. However, as Frontier was sold to sold to a consortium of investors lead by Indigo Partners, and changed its business model to an ultra-low-cost carrier (ULCC), the order stayed in a limbo, as the 160-seat CS300 is too large for Republic Airways’ operations.

The order was further questioned last February, when Republic Airways filed for bankruptcy, citing the need to eliminate turboprops and 50-seat regional jets (RJs) from its fleet, besides adjusting its capacity purchase agreement (CPA) contract with U.S. legacy carriers. The regional carrier’s restructuring plan relies now on a fleet of Embraer jetliners.

Spokeswoman Marianella de la Barrera said Bombardier removed the order from its production schedule as part of an assessment of when planes for various customers will be built.

The decision of Bombardier comes in a moment in which the CSeries program has gained momentum. In February, Air Canada committed to purchase up to 75 CS300, with conversion rights to the CS100 under certain circumstances. A month later, AirBaltic added seven additional CS300 to an existing order, and at the end of April, Delta Air Lines placed a firm order for 75 CS100, in what has been said a “game-changing” deal for the program.

Originally conceived as the Bombardier Regional Jet eXpansion (BRJX), the manufacturer relaunched the program in 2008 under the CSeries name, after a pause due to the lack of interest from potential customers. The aircraft, larger than the CRJ regional jets produced by Bombardier, was devised to compete with the Embraer 190 / 195 and the Airbus A319 and Boeing 737-700.

As of today, the CSeries has received 325 firm orders and 462 options and commitments. SWISS will be the launch customer of the CS100, which is expeted to enter into service next July 15. The CS300 is on track to receive its Type Certificate within the next six months and is scheduled to enter service in the second half of 2016.