"For now, we're still driving very hard for first flight at the end of this year," Guy Hachey, president and chief operating officer for Bombardier Aerospace, said in an interview during the Farnborough Airshow.

He said the first flight would be a key milestone that could accelerate orders for the C-Series, which represents Bombardier's (BBDb.TO) attempt to compete in the narrowbody plane market with promises of lower operating and fuel costs.

"Right now we're still fighting a little bit of 'Oh, this is a paper plane, it's unproven,'" Hachey said.

BMO Capital Markets analyst Fadi Chamoun said first flight of the CSeries could slip to 2013, saying assembly of the first plane hasn't yet begun and citing uncertainty regarding delivery of fly-by-wire systems.

"We suspect that a three- to six-month delay would not come as a shock to anyone who is following the program closely given that the company has been suggesting that the schedule is very challenging," BMO said in a note to clients this week.

Through Wednesday, the C-Series had garnered two orders during the airshow. Bombardier said Latvia-based Air Baltic signed a letter of intent to buy 10 planes with purchase rights for 10 more, and the company also announced an order of 15 planes from an undisclosed customer.

The C-Series has 138 firm orders so far, and Hachey said he expected more to come. He said the fact that Boeing and Airbus have sold out delivery slots for planes would work to the CSeries' advantage.

Hachey also said his company hoped to secure orders from U.S. airlines for regional jets, but he added those carriers were taking longer to make purchase decisions in wake of economic concerns.

"Generally I would say that the U.S. airlines are probably waiting a bit longer on their decisions," Hachey said. But once they are ready to order, "I think there's going to be huge opportunity for us in the U.S.," he added.

Shares in Bombardier (BBDb.TO) dipped on Wednesday after a new competitor won a large regional jet order that some industry watchers had expected the Montreal-based plane-maker to win.

U.S. regional airline SkyWest Inc (SKYW.O) is buying 100 regional jets from Japan's Mitsubishi Aircraft Corp, a unit of Mitsubishi Heavy Industries Ltd (7011.T).

SkyWest is the largest operator of Bombardier's CRJ regional jets and was expected to purchase more, National Bank Financial analyst Cameron Doerksen said in a note to clients.

(Editing by Mark Potter, Tim Hepher)

• A Permanent Economic Emergency