SEATTLE — Boeing closed its acquisition of Spirit AeroSystems on Tuesday, ending a process that began nearly two years ago and reabsorbing the fuselage maker into the parent company two decades after the original spin-off that created Spirit as an independent business.

The transaction closes under terms substantially modified from the structure originally announced. The most consequential modification, secured through Justice Department negotiation, carves out Spirit's existing Airbus contracting work into a separate business line that will operate at arm's length from the integrated Boeing organisation.

What the Airbus carve-out covers

The carve-out covers Spirit's existing manufacturing of components for the A220 and A350 programmes, both of which depend on capacity at Spirit facilities that have, for years, supported parallel work for Boeing programmes. The carve-out structure is designed to assure Airbus that the integration will not affect either the supply of those components or the proprietary information that flows alongside them.

The structure is unusual but not unprecedented. Similar carve-outs have been deployed in past defence-aerospace consolidations, with mixed records on whether the arm's-length protections survive the operating realities of integrated facilities.

The integration challenge

The integration challenge that Boeing now faces is substantial and is not principally about the Airbus carve-out. It is about restoring quality-control discipline to a fuselage-manufacturing operation that has, in the past three years, been at the centre of the most consequential quality incidents in the company's recent history.

Boeing's leadership has signalled that the quality-discipline question is, in their assessment, more readily addressed under integrated control than under the prior arms-length supplier relationship. The case is plausible; the execution will define whether it is correct.

The labour question

Spirit's workforce, which has been organised in ways that differ from Boeing's, transitions into the integrated company under terms that have been the subject of separate negotiation with the relevant unions. The transition framework preserves existing collective bargaining arrangements through their current cycles and provides for a structured re-negotiation when those cycles conclude.

Whether the structured re-negotiation will proceed without significant disruption is one of the operational questions the integrated company will work through over the next eighteen months. The labour environment in commercial aerospace has tightened substantially since the original spin-off; the leverage equation in the renegotiation will be different from the equation that produced the existing arrangements.

What the financials look like

The integrated company carries combined leverage that is somewhat higher than Boeing's pre-deal balance sheet but well within the range that the rating agencies had signalled they would accept given the strategic logic of the transaction. Free-cash-flow recovery, which has been the principal financial story for the parent company over the past two years, continues on the trajectory that Boeing's management has previously communicated.

Boeing's management has indicated that the integrated company will, in its first full year of operation, prioritise operational stabilisation over additional strategic moves. The framing is the kind of framing that often precedes precisely the additional strategic moves it disavows; observers will be watching closely.