By Jon Ostrower 

Boeing Co. and one of its largest suppliers on the 787 Dreamliner program are continuing talks on a deal that would raise its procurement costs on the jet, but potentially yield bigger savings on other planes under development.

The company has spent more than two years trying to hammer out new deals with Spirit AeroSystems Holdings Inc. over the price of the major parts it builds for Boeing jets, ranging from engine mountings to complete fuselages on the 737 single-aisle range.

Boeing has been pressing its suppliers to cut costs in return for more work or for more favorable terms, a crucial part of the aerospace company's effort to boost the profitability of its fast-selling commercial jets after years of heavy investment.

An interim deal with Spirit AeroSystems was disclosed earlier this year in a regulatory filing. It allows the Wichita Kan.-based company to ease earlier planned price cuts and charge more for the parts it makes for the two 787 models currently in production. It also includes a key provision that could speed a final deal for Spirit's work on Boeing's other commercial jets.

According to the filing, Spirit would record the increase in price of 787 parts as deferred revenue, and would collect "only if and when" a final agreement with Boeing is reached. Spirit AeroSystems would lose the higher pricing if a broad new pact isn't reached by the end of the year and have to return the additional higher payment difference to Boeing, according to a person familiar with the situation.

The new 787 pact follows an April 2014 deal between the companies that excluded the Dreamliner, covering only components for the current-generation 737 and long-range 777, 767 and 747 jumbo jets. The agreement, which runs until the end of 2015, also included a year-long suspension of repayments by Spirit to Boeing for an advance provided by the plane maker during the delayed development of the 787. The repayments resumed in April.

Boeing in the first quarter is estimated by analysts to have spent $26 million more on building each 787 than its average sales price, though the deficit is being reduced as production and factory efficiency have increased.

he Chicago-based company says its combined losses for the 787 are nearing $27 billion. The losses, also known as its deferred production costs, will begin to fall in 2016, when Boeing starts breaking even on each jet late this year. The program is still profitable under Boeing's accounting that allows it to spread the high early costs over 1,300 deliveries, enabling it to book future earnings today.

Central to that goal is Boeing's renegotiation of contracts with the 787's suppliers, many of whom contributed significant engineering and financial resources to develop the advanced jet and control the vast majority of the jet's costs.

Spirit AeroSystems has yet to reach a deal on its parts for a third 787 model currently in development and the 737 Max, which is beginning early production at Spirit's Wichita, Kan., factory and enters service in 2017.

A Spirit spokesman declined to detail the pricing the company had secured, but reiterated that its new agreement would be voided if a final agreement wasn't reached by year's end. A Boeing spokesman declined to elaborate.

Write to Jon Ostrower at jon.ostrower@wsj.com

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