Workers at Boeing Co. in Everett, Wash., have begun fixing a flaw on the first 787 Dreamliner test aircraft in preparation for its long-delayed first flight later this year, a Boeing executive said Wednesday. 

The modifications are expected to take about 30 days, which means the first Dreamliner could fly by late October or early November.

At the same time, the company is moving to begin test-flying the revamped version of its iconic 747 jet, now dubbed the 747-8. The first of three 747-8 test aircraft is also supposed to fly by the end of the year.

On Aug. 27, Boeing issued a revised flight-test and delivery schedule for the Dreamliner. Boeing now says the first test flight will happen sometime before the end of this year. That’s more than two years behind September 2007 date Boeing had initially envisioned for the first test flight. The company now plans to deliver the first airline in the fourth quarter 2010.

An other source close to the program said Boeing aims to have the 787 in the air by the end of November or early December.

Boeing had postponed the first flight in June, just days before the plane was to take its maiden voyage, disclosing that its engineers had found unanticipated weakness in the area where the jet’s wings are attached to its body.

The all-new Dreamliner uses super-hardened plastics more extensively than any other large jet. Such composites are stronger and lighter than metal, but behave differently when subjected to stress.

Boeing engineers testing the strength of the 787’s wings had discovered that the added force caused the composite frame to start to fray in a half dozen small locations on either side of the plane, delamination that wasn’t anticipated by its computer models. Boeing’s flight-testing was put on hold while engineers devised and tested ways to strengthen the jet.