Boeing says incorrect shim work in the aft fuselage of the 787 is limited to four locations, is “well understood” and will be repaired concurrently with other planned work.

“There is no need to conduct inspections or repairs on in-service airplanes immediately,” the company says in a statement. “There is no short-term safety concern.” Only All Nippon Airways is flying the 787.

The issue came to light in late January and concerns structures made at Boeing’s factory in North Charleston, S.C., a former Vought Aircraft facility.

The company is not saying how many of the 50-plus aircraft built so far have experienced the issue, but all will be inspected.

“We do expect to have some level of finding [of spacer issues] on assembled airplanes,” Boeing says.

At stake is the possibility of delamination in the Section 48 aft fuselage barrel of the new twin-engine jet. In some areas, Boeing found gaps between the barrel, which is a single piece of composite material—carbon fiber reinforced plastic–and the fuselage’s internal composite support structure. Small gaps are normally filled with spacers called shims to ensure a tight fit. A lose fit promotes delamination over time.

Inspections will take “several days,” and the company expects any repairs “can generally be accomplished concurrent with other planned work on the airplanes,” Boeing says.

That “other” work includes so-called “change incorporation” modifications on more than 40 787s awaiting delivery. Change incorporation refers to modifications that grew out of the 787 flight test program.

Finishing that work has gone more slowly than Boeing expected, which caused the company to miss last year’s delivery target.

Boeing says that about eight more 787s, up to about Line No. 65, will require change modifications before the process is completed. It expects to be modifying those aircraft into 2013. Tackling the aft fuselage shim issue is one more task added to that backlog of work.

But by itself, correcting the shims is not a major issue, Boeing says. “Even considered in isolation, we would expect the time to complete the repair to be measured in days, not months,” Boeing says. “This work has already started on some airplanes.”

As for any modifications to ANA’s five in-service aircraft, Boeing says they will be completed “as efficiently as possible.”