Shares in the world's No. 3 plane maker fell sharply last week after it announced a six-month delay in the inaugural flight of the 110-130-seat C-Series, its first attempt to break into a market dominated by Airbus (EAD.PA) and Boeing (BA.N).

"I think we are going to fly soon after the new year: not the 2nd (of January), but early next year," Chet Fuller, senior vice president for Bombardier Commercial Aircraft, said.

Announcing the delay from a previous goal of end-2012, the plane and train maker had blamed unspecified supplier delays for disruption to its biggest plane project.

Fuller said the problem was mainly linked to a single supplier that he declined to identify, although he hinted when answering questions that it could involve the complex process of preparing the jet's advanced digital systems for certification.

He dismissed industry speculation that the problem was linked to Bombardier's suppliers in China, where the Canadian firm extended a marketing agreement with state-owned COMAC at this week's international air show in Zhuhai, near Hong Kong.

He broadly exonerated a production plant in Northern Ireland that is responsible for the plane's carbon-composite wings.

"There is some schedule pressure there on the wing. A while back there was some schedule pressure in other areas," he said.

"At this point of any programme, something is always competing for first place (on delays). Right now, it is one particular supplier who is solidly in the lead," he added.

Analysts say that with the latest delay, Bombardier faces an even tougher sales job. Orders for the jet, which is priced significantly cheaper than its rivals' planes, have slowed with just five so far this year. In total, it has only 138 firm orders.

COMPETITION FOR RESOURCES

Fuller said the C-Series would break new ground in digital architecture and that this posed particular problems in getting ready for safety certification, given the "reams" of paperwork required to log each line of software for inspectors.

"These airplanes are now controlled by hundreds of millions of lines of code -- and not simple lines of code. Just when you think you couldn't possibly have a simultaneous and multiple failure someone proves you can," Fuller said.

"The certification authorities really have no interest in programme performance and every interest in safety. For the flying public that is a good thing, but it does make programme performance a challenge."

The problem of applying a decades-old airworthiness process to the digital revolution now sweeping through plane design contributed to a four-year delay to Europe's A400M military airlifter, as engineers struggled to track engine software.

So far, the C-Series delays are nowhere near as serious as for the Airbus military airlifter or Boeing's 787 Dreamliner, which entered service three years late, but analysts say sales of the aircraft could remain subdued until its first flight.

Bombardier expects deliveries of the 110-seat CS110 version of the C-Series to start in mid-2014. The entry into service for Bombardier's 130-seat CS300 is still seen at the end of 2014.

Although it is new, Bombardier's $3.4 billion plane project faces problems shared by many aircraft manufacturers.

A global supply base is trying to cope with production increases in most major civil programmes and some military ones like America's F-35 fighter just when credit remains scarce.

"Everyone is competing for resources, for capability, for intellect, for attention. So you have got to keep the pressure on constantly and somehow make sure you get truth data out of all your suppliers," said Fuller in an interview.

"You have got to treat them like partners because yelling at people doesn't do any good or make people move faster."

Bombardier does however have to deal with one requirement yet to be tackled by its competitors, according to Fuller.

On Christmas Day 2009, a bomb hidden in the underwear of Umar Farouk Abdulmutallab caused a fire but failed to explode on a Delta Airlines flight carrying 289 people.

That led to what Fuller described as the 'underwear bomber rule', forcing designers of new aircraft to prove the fuselage could withstand a limited amount of damage without crashing.

"So now you have to route things like hydraulics and electrical and fuel systems down both sides of the airplane. That is how a fighter is designed for battle damage," said Fuller, a 51-year-old former U.S. Navy pilot.

"The C-Series is the first airplane to have to comply with it, as will every other airplane in the future. So now someone has to determine sufficient tests. It is a complex business and keeping it ... all on schedule is very challenging." (Editing by Jeremy Laurence)

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