By Valerie Insinna

CHARLESTON, South Carolina (Reuters) - Boeing Co has increased production of its widebody 787 Dreamliner from three to four planes per month as it gets ready to ramp to five a month by the end of the year, a company official said on Tuesday.

The U.S. planemaker also plans to add a second production line to the company's facilities in Charleston, South Carolina, as it completes work this year on inventory 787s that are being modified at the site to meet U.S. Federal Aviation Administration standards, said Lane Ballard, Boeing's vice president and general manager for the 787 program.

The modification involves fixing miniscule gaps in the forward pressure bulkhead that exceed specifications.

Boeing's plant in Everett, Washington, where 787s also are being modified to meet FAA standards, will continue doing that work, Ballard added.

Ballard announced the rate increase as reporters toured the company's Charleston production facility two months after Boeing announced a large order for almost 200 Dreamliners.

In April, the company said it had stabilized 787 production at three jets per month after producing Dreamliners at a lower rate earlier in the year. Boeing previously said it plans to deliver 70-80 of these jets in 2023.

(Reporting by Valerie Insinna in Charleston, S.C.; Editing by Will Dunham and Sharon Singleton)