A “systems issue” that requires a software update is pushing back the first flight of Bombardier’s Learjet 85 once more, the company says.

Bombardier is not putting a timeline on how long that update will take nor when it expects its all-new composite Learjet to fly.

The company was in final preparations for first flight, receiving a flight-test permit from FAA late last month. At the time, the company said it was finalizing the aircraft’s configuration and conducting further engine runs and high-speed taxi tests in preparation for the first flight. The company had hoped to fly the aircraft in March.

Bombardier quietly rolled out the aircraft to its employees in September, but President and CEO Pierre Beaudoin had said first flight awaited the completion of systems integration. The company wanted to ensure the systems “responded the way they should,” Beaudoin had said during the company’s first-quarter earnings call. The company is not specifying the systems involved that are responsible for the latest holdup of the flight test program.

The flight has already been delayed by at least a year as Bombardier ironed out problems with the composite program – its most expansive on any of its aircraft yet. Beaudoin had acknowledged that “[it was] a little challenging to get all the composite programs done and produced, [but] that’s all behind us now.”

The company has not yet outlined a certification timeline, planning instead to build up experience flying the Learjet 85 “for a period” before setting a schedule. This is a similar approach that the company took in establishing a timeline for the CSeries.