Boeing Co. promised to deliver the first 787 Dreamliner by September as planned and ship as many as 20 this year as mechanics rework finished planes to meet new specifications.

Dreamliners will need to be modified through next year in the “factory within a factory” set up in Everett, Washington, where Chicago-based Boeing builds all its wide-body jets, Chief Executive Officer Jim McNerney said today on a conference call.

Boeing is working toward a third-quarter delivery target for the first 787 after seven delays. The fixes include replacing some fasteners as Boeing accommodates design changes made during the testing process for the plastic-composite jetliner, which is running three years behind schedule.

“There’s no mystery to getting it done,” McNerney said. “We understand the work statement, the fix, the work-around, the change that has to be made, and it’s a matter of scheduling it and getting it done.”

McNerney commented after Boeing’s first-quarter profit beat analysts’ estimates, buoyed by military jet earnings that helped blunt declines in the commercial airplanes business at the world’s largest aerospace company.

Net income rose 13 percent to $586 million, or 78 cents a share, surpassing the 70-cent average estimate of 21 analysts surveyed by Bloomberg. Boeing climbed 72 cents to $76.20 at 12:29 p.m. in New York Stock Exchange composite trading, the highest intraday price since June 2008.