Boeing has halted deliveries of its 787 Dreamliner just two months after restarting them.

The Federal Aviation Administration said it hasn’t finalized approval of Boeing’s process to inspect and fix manufacturing quality defects that were discovered last year at the 787 fuselage joins.

FAA spokesperson Crystal Essiaw wrote via email that Boeing has “proposed a revision to the existing inspection process for previously assembled aircraft,” and that any such change to the quality verification procedures “must be validated and approved by the FAA.”

She said “Boeing made the choice to stop deliveries of previously assembled aircraft” while it awaits FAA approval.

The FAA had already cleared Boeing to resume 787 deliveries in late March and Essiaw said “there have been no new discoveries” to cause further concern.

This suggests that it may just be a matter of finalizing the documentation of Boeing’s inspection and verification procedure — a “show us your homework” situation, rather than the solution not being acceptable.

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In a statement, Boeing said “We are working to provide the FAA with additional information concerning the analysis and documentation associated with the verification work on undelivered 787s.”

Boeing added that “there is no impact on the in-service fleet.”

The jet maker is depending upon deliveries of the 787, along with its single-aisle 737 MAX, to provide much-needed cash flow during the aviation downturn.

About 100 Dreamliners accumulated on the ground when deliveries halted between early October and late March. Late last month, with just a dozen of those planes delivered to airlines, Boeing’s leadership told Wall Street it anticipated delivering the majority of the rest this year.

It’s unclear how long it will be before deliveries can restart.

Machine-induced flaws in the fuselage

The initial halt to 787 deliveries last October was due to the discovery of two separate defects in manufacturing the fuselages.

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One was discovered in 2019: A software flaw was causing Boeing’s machines to fabricate wrong-sized shims — the small pieces of material that are precisely sized to fill gaps at the joins.

Then last August, Boeing discovered that the machines that fabricate the carbon composite outer skin of the airplanes were producing an unacceptable lack of smoothness at the fuselage joins.

On planes with both defects, Boeing could not guarantee structural integrity. As a result, last August eight such 787s that had already entered airline passenger service were grounded, and inspections began to find the full extent of the issue.

At first, the problem was thought to be only with the join at the aft fuselage of the plane, but the concerns broadened to include more joins all over the fuselage.

Boeing didn’t resume deliveries until late March as it inspected hundreds of aircraft.

Because the inspection process was so disruptive, requiring mechanics to take apart the airplane interior to reach the structural joins in the fuselage, Boeing used statistical sampling to narrow down the areas where it needed to focus the inspections.

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The FAA’s Essiaw wrote Friday that “as part of Boeing’s ongoing analysis of the shimming issues,” the jet maker is “finalizing a proposed corrective action which would allow them to show compliance using statistical analysis for specific areas of the aircraft.”

This is what the FAA hasn’t yet signed off on.

As part of the FAA’s heightened scrutiny of Boeing, when 787 deliveries resumed in late March it insisted on having its own inspectors sign off on the airworthiness of the first four jets to be delivered, including three that went to United Airlines.

But after those initial four planes, the FAA delegated that authority back to Boeing.

Essiaw said that every 787 delivered was inspected to ensure it complied with all regulations.

“All aircraft delivered are safe,” she wrote.