MIRABEL, Que. Bombardiers CSeries commercial aircraft is set to take off on its maiden flight this morning.

The gleaming white CS100 plane is scheduled to lift off the runway at Mirabel airport north of Montreal at around 9:30 a.m. as weather clears.

Heavy dark clouds were slowly moving away from the airport after early morning rain ended.

Hundreds of employees, suppliers and invited guests are expected to watch the plane leave the ground for the first time. The public and Bombardier employees around the world can witness the event via webcast at www.cseriesfirstflight.com.

The plane will take off after a Global 5000 chase plane passes along the flight route.

The business jet will then fly in parallel to the CSeries to convey any observations to its two pilots and flight engineer.

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The test flight could last between 45 minutes and three hours and is scheduled to be followed by a news conference after pilots provide officials with a debriefing.

The flight will begin a year of testing, leading to delivery of the first aircraft.

The first 110- to 125-seat CS100 is slated to enter into service in about a year, barring more delays.

The heavily anticipated first flight had been delayed three times over nearly nine months.

The plane is made of composite materials and its Pratt & Whitney engine promises to be quieter and help deliver fuel cost savings for customers.

The larger CS300, with up to 160 seats, is slated to be delivered by the end of 2014, after undergoing its own test flights.

Bombardier has received commitments for 388 aircraft, including 177 firm orders.

The company has said it expects to secure at least 300 firm orders from 20 customers by the time the first CSeries is delivered.