While inspecting and reworking undelivered 787 Dreamliners for the flaws at fuselage joins that emerged last year, Boeing has discovered a new manufacturing quality problem with a key structural part in the nose of the aircraft.

In yet another serious setback as Boeing struggles to recover from the pandemic’s impact on production, its engineers have now found unacceptably large gaps around the forward pressure bulkhead.

This is a hefty, dome-shaped structural barrier forward of the pilot instrument panel that’s crucial to maintaining air pressure within the cockpit and passenger cabin.

The additional inspections and repairs now required will prolong the current 787 delivery halt and extend the duration of the large inventory buildup. In addition, it has forced Boeing to cut the already slow production rate further.

“Boeing is reprioritizing production resources for a few weeks to support the inspection and rework,” the company said in a statement. “As that work is performed, the 787 production rate will temporarily be lower than five per month.”

Boeing insists the gaps around the bulkhead are tiny — measured in thousandths of an inch — and the Federal Aviation Administration concurs with company engineers that it is “not a safety-of-flight issue.”

However, the gaps are beyond the tolerances demanded in the design specification for the 787, and so the backlog of about 100 completed planes that are parked and undelivered must be inspected for the flaw and potentially repaired.

Boeing and the FAA are still assessing whether similar inspections will be needed for the in-service fleet currently flying passengers around the globe.

“The FAA is aware of a manufacturing quality issue near the nose on certain 787 Dreamliners in the company’s inventory of undelivered airplanes,” the federal agency said in a statement. “Although the issue poses no immediate threat to flight safety, Boeing has committed to fix these airplanes before resuming deliveries.”

“Based on data, the FAA will determine whether similar modifications should be made on 787s already in commercial service,” the statement adds.

In a statement, Boeing said it was engaged in detailed discussions with the FAA on verification methodology for 787 fuselages, and conducting associated inspections and rework. In connection with these efforts, the company has identified additional rework that will be required on undelivered 787s

The discovery has forced Boeing to take teams of mechanics off 787 production to add resources for the inspections and rework on undelivered jets.

Thwarting its efforts to generate cash flow with the 787, Boeing said it now cannot meet its target of delivering more than half of those parked planes this year.

A spokesperson said the decision to cut the production rate is only partly due to diversion of resources to deal with the new manufacturing problem. Another factor is the lack of interest from long-haul airlines in taking 787 deliveries because of the continued steep drop-off in international air travel.

This new manufacturing flaw complicates an already difficult recovery for the 787 program.

The FAA has not yet approved Boeing’s inspection process for the previously discovered fuselage flaws. The agency is demanding analytical data on Boeing’s proposal that it not inspect every airplane, but instead inspect a select sample of the planes.

These inspections are laborious, requiring mechanics to take apart some of the interior sidewalls to see the joins. Until the FAA verifies that the proposed sampling protocol is acceptable, Boeing cannot deliver any of the jets.

The new flaw adds one more thing to be inspected and will lengthen the FAA approval process.

Boeing did manage to deliver one 787 last month, the first handover of that jet in more than five weeks. However, that plane was an exception. It had been parked since last fall, prior to the initial delivery halt last October, at the request of the customer, Turkish Airlines.

From last fall, 787 deliveries were stopped until March, when Boeing developed its inspection and repair protocol and the FAA gave its initial approval to resume deliveries.

But when the FAA demanded more data on Boeing’s proposal to conduct further inspections by sampling, deliveries stopped again in May.

During that brief respite between March and May, and with the single plane Turkish took in June, Boeing has delivered just 14 Dreamliners in the nine months since last October.

Now the paralysis in deliveries is set to be prolonged further.

The only good news for Boeing recently has been that sales of the 737 MAX have picked up.

Data released early Tuesday shows Boeing won 219 orders in June: the 200 MAXs booked by United, plus 18 widebody 767 freighters and one large 777 freighter, all for FedEx.

However, 71 MAXs were canceled as well as two 737 military derivative planes, so the net orders for June came to 146.

In addition, Boeing removed another 49 MAXs and seven 787s from its firm order backlog, which means those orders are now considered too dubious to count as firm due to customer financing or contract issues.

Subtracting those, June produced a net increase in firm orders of 90 airplanes.

Deliveries were not so robust. The 45 jets delivered consisted almost entirely of single-aisle MAXs plus twin-aisle, widebody freighters and military refueling tankers.

Boeing delivered 33 MAXs in June, along with two 737-based P-8 anti-submarine jets for the Navy.

It also delivered 10 of the larger twin-aisle jets. But with international air travel still moribund, only two of those were passenger planes: the 787 built last year that went to Turkish and a 777-200LR for Turkmenistan.

Six of the widebodies were freighter models. Two were air-to-air refueling tankers, one for the U.S. Air Force and one for the Japanese air force.

That brings Boeing’s deliveries so far this year to 156 airplanes.