Boeing reported positive initial results Sunday from a test in which engineers bent the wings of a 787 Dreamliner ground test airplane until the load was more than one-and-a-half times anything the jet will experience in service.

In a carefully planned extreme test inside Boeing’s Everett plant Sunday, engineers bent the wings of a 787 Dreamliner ground-test airplane until the load was more than one-and-a-half times anything the jet will experience in service, the company said.

Boeing said “the initial results … are positive,” but that it could take several weeks of analysis before the test is declared a success.

The “ultimate load” wing stress test is a dramatic milestone in the process of obtaining Federal Aviation Administration (FAA) certification so the airplane can be used for passenger flights.

By the end of the test, the wing had deflected upward from the horizontal by about 25 feet, Boeing said in a statement.

Engineers had decided in advance not to continue to bend the wings until breaking point, as they’ve done on past airplane programs.

The test was performed on one of two ground-test airplanes that will never fly.

The plane sits in a large framework inside the plant.

Measuring devices are positioned on the Dreamliner’s airframe and cables run from the structure to hanging weights that create the loads.

In the ultimate load test, the cables pulled the wing slowly upward, gradually building over more than two hours toward the crucial 150 percent mark.

In a similar test in January 1995, Boeing bent the wings of the 777 beyond ultimate load until they broke in an explosive burst at 154 percent of the anticipated in-service maximum load, destroying the test plane.

Boeing spokeswoman Lori Gunter said Boeing this time would be satisfied with passing the 150 percent certification threshold.

Unlike the 777 wings, which are traditional aluminum, the Dreamliner’s wings are made of more flexible carbon-fiber-reinforced plastic and would be expected to keep bending without breakage far beyond the certification mark.

“We don’t intend to break” the Dreamliner’s wings, Gunter said.

“There is no requirement to (do so) and the loads required are quite high, so we don’t intend to expose our people or equipment when it is not necessary.”