Boeing will hold the 747-8 line in place from 6 May until 7 June, to allow it to catch up on design changes as it introduces the new -8I passenger model into its production system.
The company's 2011 delivery target, however, remains unchanged despite it evaluating an effect on its delivery schedule.
"The process of starting up the regular production of the 747-8 Intercontinental has created some challenges best addressed at this early stage in the ramp-up," said Boeing.
Boeing is ramping up 747-8 output from 1.5 to 2 aircraft per month, with the goal of reaching that target in 2012. It will hold the line from advancing over the next month in favour of incorporating design changes from flight test and completing unfitted work inside the factory.
In recent weeks, programme sources say the number of assembly tasks, or jobs, has continuously crept up, even as additional machinists have been moved to the factory floor to tackle the unfinished work.
Despite holding in place the line for a calendar month, Boeing still intends to deliver between 12 and 20 747-8s in 2011, the first freighter mid-year and the first passenger model by year end.
The company told the Seattle Times it is "evaluating the effect on the delivery schedule" for those aircraft to follow after first 747-8F delivery in 2011. However, it told Flightglobal: "We're staying close to our customers to make sure they understand our manufacturing and delivery plans."
Atlas Air, the largest 747-8F customer with 12 on order, said in its 3 May earnings statement it planed to "receive and place into service three 747-8Fs from Boeing in the beginning of the fourth quarter of 2011". The cargo operater, however, added: "To date, we do not have a final delivery schedule agreement with Boeing."
Boeing has rolled out 20 747-8s to date, including two -8I test aircraft, and five -8F test aircraft, all currently participating in flight test. The balance are production freighters now occupying spots on the company's Everett, Washington flight line.
Including the final fuselage and wing body join position, Boeing has another three 747-8s in the final assembly process, while accommodating additional aircraft in various states of assembly from wing and fuselage build up, to systems installation and wing stub join spread across the factory's 40-21 and 40-22 buildings.
"Completing this work in the factory also will ensure that airplanes travel to the flight line in the most complete state possible, and minimise work required on the flight line," added Boeing, which plans to use its Global Service & Support facility in San Antonio to conduct refurbishment of its flight test aircraft.