Bombardier Aerospace says it's taking longer than anticipated to prepare the new CSeries commercial jet for its first test flight.

The Montreal-based company had been aiming for the first flight by the end of July but now says it will occur "in the coming weeks" without giving a target date.

Bombardier says the highly technical work is progressing smoothly but it will take more time to validate the overall systems and software integration.

The CSeries is a critical new generation of planes for Bombardier Inc., which is Canada's largest aerospace company and the world's third-largest maker of passenger aircraft after Boeing and Airbus.

The first flight of the CSeries had previously expected by the end of last month but Bombardier announced June 26 it would was delayed until the end of July.