Boeing cut the production rate on the 747-8 jumbo jet, its biggest and most-expensive model, citing dwindling demand for the largest passenger planes and freighters.

Monthly output will drop by early 2014 to 1.75 aircraft from two now, Boeing said Friday. The company said the change in tempo, to 21 jets a year from 24, isn’t expected to have a significant financial impact.

Boeing had previously warned production rates might not be sustainable amid weakness in the global air-cargo market. Four-engine planes such as the 747-8 and the Airbus A380 also have seen their popularity dwindle as airlines opt for the biggest twin-engine models instead.

“The passenger variant’s got five years on the market at most,” said Richard Aboulafia, vice president of Teal Group, an aerospace forecaster that has done work for Boeing. “The market for large quad jets is small, and getting smaller.”

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Boeing has won just 110 orders for the 747-8, of which only 40 are for the passenger version, since it began offering the plane in 2005. During that time, carriers ordered more than 700 777s, the company’s largest twin-engine jet. Those models are more fuel-efficient than those with four engines.

The 747-8 is Boeing’s costliest commercial plane, with list prices of $351.4 million for the passenger version and $352 million for the freighter. It entered service in 2011.

Boeing said it will continue to monitor market conditions for jumbo jets and their effect on production rates. The global air-cargo market should resume growing at long-term average rates in 2014, Boeing said.

“If there is no pickup in orders we could see further cuts to the 747-8 production rate,” wrote Rob Stallard, a London-based analyst at RBC Capital Markets.

Twin-engine models like the 787 Dreamliner able to fly longer routes have eroded the need for four-engine planes in serving intercontinental markets. Boeing’s promise to come out with a successor to its best-selling 777, the 777X, also threatens to choke off any potential interest in the 747-8, Teal Group’s Aboulafia said.

Boeing would be smart to postpone any decisions until the cargo market recovers, he said.

“This is the worst time to make a long-term decision about the plane, because for the last two years, we’ve had really bad cargo numbers,” Aboulafia said.

Bloomberg reporter Andrea Rothman in Toulouse, France, contributed to this report.