Bombardier Inc (BBDb.TO) said on Tuesday it was reviewing 2017 delivery plans for its CSeries jets, after U.S. engine parts maker United Technologies said it was resolving issues with its geared turbofan (GTF) engines to make them more durable.

United Technologies Corp (UTX.N), the maker of Pratt & Whitney jet engines, held back some GTF shipments to plane makers and offered spares to airlines, which had faced problems with engines already in service.

"Bombardier is working closely with Pratt & Whitney to evaluate and mitigate any potential impact on its customers and will provide a full update on November 2, when it issues its Q3 results," spokeswoman Nathalie Siphengphet said by email.

Both Bombardier and Airbus SE have faced delayed deliveries of separate GTF engines.

Airbus Chief Executive Tom Enders said recently that Pratt's engine has "tremendous potential" despite initial "teething problems." The European plane maker is taking a majority stake in the CSeries program.

"Pratt is working very hard to iron these out for our A320 family as well as for the CSeries," he told Reuters in Montreal.

Montreal-based Bombardier has forecast deliveries of about 30 CSeries jets this year, but has only delivered 12 so far, raising questions about the company's ability to meet its guidance.

"We've got some supplier challenges so you know, we'll see how the ramp up goes," Bombardier Commercial Aircraft President Fred Cromer told Reuters on Friday. He did not provide names of suppliers.

Korean Air Lines Co Ltd, which was to take delivery of its first Bombardier CSeries in the coming weeks, has had an order of five jets delayed.

"The detailed schedules to introduce the models have not been decided," said a spokeswoman for Korean Air Lines in Seoul who declined to explain the delay. "We are in continued talks with the manufacturer."

Two sources familiar with the matter said Pratt & Whitney was delayed in producing a corrected engine liner required for the Korean deliveries.

In April, Bombardier said Pratt would issue the liners for the engines in Korean's order for delivery this past summer.

At the time, Bombardier instructed CSeries operators Swiss International Air Lines and airBaltic to inspect their engine combustion liners after 2,000 flight hours. Pratt & Whitney said it had added a combustor lining inspection to its regularly scheduled maintenance of the engine.

A Pratt spokesman referred questions about Korean's deliveries and the engine liners to the carrier.