The innovation risk
The 787 involved not merely the outsourcing of a known technology. It involved major technological innovations unproven in any airplane. Would the carbon fiber composite survive the rigors of international flying? Could lithium-ion batteries, which are notorious for overheating and causing fires that are difficult to put out, be safely used? No one knew for sure. The 787 also contains multiple new electrical systems, power and distribution panels. The interactions among these novel technologies, introduced simultaneously, also exponentially increased the risk of innovation.
The innovation risk implied a greater involvement by Boeing in the development and manufacture of the aircraft. Astonishingly, Boeing opted for lesser involvement, delegating much of the detailed engineering and procurement to sub-contractors. The result? Unexpected problems have kept occurring that have delayed the project and increased its cost