"Our timing on a decision to offer that airplane has not changed," Boeing Commercial Airplanes President Ray Conner wrote in a message to employees Thursday. "We are absolutely committed to the 777X and continue to invest the necessary time and resources to ensure we produce a superior airplane for our customers."
The development of a stretch version of the Dreamliner, called the 787-10X, continues as well, Conner wrote.
Citing unidentified people familiar with the matter, The Seattle Times reported earlier Thursday that Boeing had slowed down the development process.
Boeing's former commercial president, Jim Albaugh, had talked earlier this year about taking a plan for selling the wide-body jets to the board for approval by the end of 2012. In June, Boeing executives begin talking up the 787-10X, indicating that plane has a more "straightforward statement of work."
After Conner was appointed June 26, he said the plan will be presented once it's ready, comments that were repeated in Thursday's message.
Boeing's rival, Airbus, plans to introduce the A350-1000 in 2017 to compete with the 777 and 787.
Major Boeing 777 and 787 customers have voiced concerns over the Chicago-based jet maker's waffling on the two programs. Cathay Pacific, a loyal 777 operator, opted to order Airbus A350-1000s earlier this year.
"That was a predictable event, and more defections are likely" if Boeing continues to dawdle on the 777X and 787-10, analyst Richard Aboulafia, with the Teal Group, noted in a monthly update.
Boeing has talked about upgrading the popular Everett-built 777 with new engines and composite wings though has not committed to a design. The 787-10 would be Boeing's largest version to date of the mostly composite Dreamliner and is expected to seat between 300 and 350 passengers.