Boeing identified a structural issue with the 787 several weeks ago but it was not until last Friday that analysis confirmed that the first flight should be delayed pending a modification.
"Preliminary analysis was that we could have a credible flight-test envelope, but then during detailed analysis the envelope narrowed to the point that it would not be useful for flight-test," says Boeing Commercial Airplanes chief executive Scott Carson.
Speaking during a conference call today to explain the latest crisis to hit the Dreamliner programme, Carson said that the revised schedule for first flight and the impact on deliveries will be made public "in the next several weeks".
© Jim Larsen
He expects the maiden flight delay to have an impact on first deliveries, which are currently scheduled for the first quarter of next year.
Pat Shanahan, vice-president and general manager of airplane programmes, says that the modifications required to address the structural problem "are manageable".
The 787 programme general manager, Scott Fancher, says "several possible modifications" have already been identified and, once the final version is chosen, the airframer will proceed with detailed design and verification on the static test airframe and the first flight-test aircraft.
"The area in question is a few square inches in the side of body. The modifications are relatively small without very much weight [penalty] and a negligible impact on performance."
Shanahan says that the area affected is in the upper region of the wing, centre section and body join, where there are multiple structures and materials including aluminium, titanium and composites. Both aluminium and titanium is being evaluated for the modification package.