NEW YORK (Reuters) - Boeing Co delayed its 787 Dreamliner for the third time yesterday, pushing the programme about 15 months behind schedule, as it makes slow progress on assembling the revolutionary carbon-composite plane and continues to grapple with underperforming suppliers.

The delay was at the low end of Wall Street's expectations, as the US plane maker had already admitted to problems with late redesigns of the new aircraft and the amount of work being done at its Everett, Washington, plant that should have been completed by suppliers.

Boeing shares, which had plunged 30 percent since last summer on worries about the 787, were up $3.69 or 4.9 percent to $78.71 in afternoon trading on the New York Stock Exchange.

"It appears that Boeing has finally produced a realistic timetable, even if first deliveries are now five quarters delayed from their initial schedule," said Michael Derchin at FTN Midwest Securities Corp in a research note. "Execution of the new plan is critical and any slippages from here would be negatively received."

Boeing's plan was to outsource almost all major manufacturing to outside companies and then assemble the plane in Everett. It has since found that such a decentralised structure makes it hard to keep a check on suppliers' mistakes and delays.

Despite problems, the 787 is still the most successful launch in Boeing's history in terms of sales, racking up orders for 892 planes worth more than $145 billion at list prices.

The latest delay means Boeing will have to compensate airlines for late deliveries, but it has not put any figures on how much that could cost.

"It's too early to tell who will and who won't be affected by penalty payments," said Scott Carson, chief executive of Boeing's commercial airplanes unit, on a conference call.