An aircraft flies over the Bombardier plant in Montreal. (Paul Chiasson/Canadian Press)

With the hiring of 300 additional engineers, Bombardier (TSX:BBD.B) will be halfway to filling the jobs required to build its new CSeries aircraft.

The Montreal-based aircraft manufacturer is adding the jobs while it finishes laying off about 4,360 employees because of the slowdown in business jet orders.

The new hires are slated to be on board by June before the focus turns to hiring personnel for airplane testing and assembly.

Robert Dewar, a vice-president of the CSeries program, said Monday that the economic slowdown has facilitated the hirings of qualified workers.

"We thought a year ago, before the economic crisis, that it was one of the main risks on the program," he said Monday during a media tour of the main research and design facility. "And actually, with the economy the way it is, it's perfect timing actually to get the skilled people we need."

Dewar said aerospace workers, who often shift jobs every seven years, are eager to sign up for a new aircraft program like the CSeries.

"It's a very, very exciting program to work on. It's all-new technology, so for engineers to be at the forefront of new technology in aerospace is really exciting."

New graduates represent another 10 to 15 per cent, foreign hires 10 per cent and workers from the rest of Canada the remaining five per cent.

Suppliers also have 360 workers on site helping to develop the 110- to 145-seat aircraft that is slated to enter service in 2013.

Bombardier will official break ground Tuesday on its new testing facility in Mirabel, north of Montreal.

About 1,200 people — 1,000 in Montreal and 200 in Belfast, Northern Ireland — already work on the new aircraft, which promises to burn 20 per cent less fuel and save up to 17 per cent on cash operating costs.

Meanwhile, Bombardier said it is confident it will succeed against a second complaint filed by Brazilian rival Embraer SA over grants provided by the British government.

Benjamin Boehm, vice-president commercial aircraft, said the British government successfully defended itself this summer against a first complaint filed by Embraer.

A preliminary ruling said the financial assistance fell within World Trade Organization rules.

"We take everything that they bring to the EU or elsewhere extremely seriously but at the same time the U.K. government has proven very well that everything that they're doing is within WTO regulations so we're confident that it will be proven again that we're following WTO," he told reporters inside a mock-up of the new plane.

Britain has committed lending $202 million to support jobs building the CSeries wings.

Ottawa has promised a loan of up to $350 million, while the Quebec government has earmarked $117 million.