In a statement late Thursday Boeing said it had "identified a workmanship issue" with the horizontal tail, also called a stabilizer. Shims and fasteners weren't installed correctly, the aircraft maker said. The stabilizer, the smaller wing on the plane's tail, is built by Italian manufacturer Alenia.
Boeing said inspections will take one to two days. Any work required will take up to eight days for each plane.
Boeing said it will not fly five flight-test jets until they are inspected. Boeing has produced 23 in total. It also said the program remains on track - the first 787 remains scheduled for delivery by the end of the year to ANA.
The Seattle Times reported Thursday that the problem in the stabilizer was found within the past week.
The problem is "regrettable but under control," Boeing spokeswoman Yvonne Leach told The Times. "We made a decision to be prudent and do the inspections first."
Of the five flight-test planes, the Times said Planes 2 and 3 were due to fly in the next few days while the other three are in ground tests or preparing for future tests.
The Times said workers at Boeing's assembly plant in Everett discovered the problem with shims, which fill small gaps during assembly.
"Shims were improperly installed in a manner that could lead to lower-than-expected longevity for a joint within the horizontal stabilizer," Leach said.
Boeing has relied on suppliers from around the globe to build nearly all components of the 787, but the program has been hampered by ill-fitting parts and other glitches. December's first flight was more than two years behind schedule.
In May, Boeing reported a design flaw in a bracket in the plane's tail and said it would change the way the device is made. The areas affected were made by Korea Aerospace Industries Ltd., and Boeing's Charleston, S.C., plant.
In late April, Boeing told suppliers to stop delivering 787 parts to Everett for 24 manufacturing days, saying some manufacturers were having trouble getting components and some needed to finish engineering and design changes Boeing wanted.