Nov. 4 (Bloomberg) -- Boeing Co., the world's second-largest commercial-aircraft maker, said it needs to replace about 3 percent of the fasteners used to hold together sections of the new 787 Dreamliner test jets because they were installed incorrectly.

All four 787 jets in final assembly in Everett, Washington, were found to have some fasteners improperly installed. Mary Hanson, a spokeswoman for Chicago-based Boeing, said in an interview today. She declined to project how long it will take to correct the problem.

The 787 Dreamliner is Boeing's most successful new jet launch ever with about 900 sold before the plane has ever flown. The 787 has been delayed three times due to parts shortages and problems with the new production process, which uses suppliers around the world to build large sections of the plane for assembly in Everett. The plane was already 15 months late before an eight-week-long machinists' strike that ended Nov. 2.

``Most investors anticipated further slippage in the 787 schedule because of the strike,'' Rob Stallard, a New York-based analyst with Macquarie Research Equities, said in an interview today. ``The fastener issue doesn't help at all but the strike is probably bigger for first flight and delivery.''

The company is now studying the impact of both the strike and the fastener replacement on the 787 schedule, Hanson said, adding she didn't know how long that review would take.

Before the strike, Boeing had said it was aiming for first delivery in the third quarter of 2009. Stallard said he is currently projecting 787 deliveries to begin in the first quarter of 2010.

787 `Disappointment'

``We've become accustomed to disappointment on the 787,'' Stallard said. ``It's the way things have been on the program for a while.''

In some cases, the fasteners were installed to incorrect lengths, either longer or shorter than the specifications called for, Hanson said. As a result, in some places there is a gap between the head of the fasteners and airplane surface, so they don't lie flat, she said.

``The issue is with installation of the fasteners, not the fasteners themselves,'' Hanson said.

After finding improperly installed fasteners on the four test jets at its manufacturing hub in Everett, Boeing notified partners assembling sections of the aircraft, who identified the same problem on pieces that were still being assembled, she said, without naming any of the suppliers.

Boeing gained 92 cents, or 1.7 percent, to $53.77 at 12:28 p.m. in New York Stock Exchange composite trading. The stock had dropped 39 percent this year.

To contact the reporter on this story: Edmond Lococo in Boston at elococo@bloomberg.net.

Last Updated: November 4, 2008 12:40 EST