Manufacturing lines for the BellBoeing V-22 Osprey and CH-47 Chinook resumed production today after a five-day hiatus.
The Defense Contract Management Agency has informed Boeing that it has "fulfilled the necessary requirements to return to production status," a company statement says.
"Boeing Rotorcraft Systems cooperated fully with its customer in order to resolve this matter and will continue to work diligently to maintain the highest standards of quality and product integrity," the statement adds.
Boeing has not disclosed what specifically caused shutdown at the plant near Philadelphia, but local news reports have again raised the possibility of sabotage.
A plastic cap was found in a V-22 fuel line during a DCMA quality inspection, which prompted the shutdown, according to media reports.
The incident comes six months after the same plant was shutdown after a disgruntled employee sabotaged a CH-47 by cutting a bundle of wires. Another helicopter was also found damaged on the same day, but authorities never identified the source.
Boeing builds the fuselage for the V-22 in Philadelphia. The structure is shipped to Amarillo, Texas for final assembly by Bell.
The CH-47F and MH-47G is also assembled in Philadelphia, which is one of Boeing's two hubs for rotorcraft production. Boeing also assembles the AH-64 Apache in Mesa, Arizona.