(Reuters) – Rain and cloudy weather is forecast for Bombardier Inc’s flight test site for much of this week, casting doubts over the date for the first flight of the Canadian company’s all-new CSeries jetliner.

The 100- to 149-seat CSeries is the first completely new narrow-body aircraft in its class in decades, and is Bombardier’s attempt to break into a market dominated by Airbus and Boeing Co .

Bombardier, the world’s fourth-largest plane maker, has said weather will be the main factor in deciding when the new plane will fly, an event that will help determine whether the CSeries will meet its manufacturers’ promises on performance and efficiency.

The company has given no date for the first flight, although a source familiar with the situation has tipped September 17 as a likely deadline.

In a sign that the first flight might be only days away, Bombardier on Friday began high-speed taxi trials at its test site at Mirabel, Quebec, and said a few more runs were planned. That includes taxi tests expected to go up to 120 knots, conducted in optimal weather, good wind conditions and a dry runway.

More tests on the test plane, known as FTV1, took place on Monday, according the plane-tracking website planefinder.net as well as live broadcasts of air-traffic control communications on liveatc.net.

Social media reports from people following the runway tests said the plane completed several taxi trials up to 120 knots. Bombardier could not immediately be reached to comment.

Environment Canada forecasts rain at Mirabel airport, some 50 km (30 miles) north of Montreal, for Tuesday, Thursday and Friday, and cloudy weather on Wednesday. The weather is expected to turn sunny by Saturday.

Environment Canada showed good wind conditions at Mirabel on Monday, but mostly cloudy weather.

(SOURCE REUTERS)