Boeing Co has warned of delays in deliveries of its 787 Dreamliner as three separate production flaws over the past year hamper efforts to develop an alternative cash cow to its grounded 737 MAX.

In the latest issue, Boeing learned during fabrication of the 787 horizontal stabiliser that some components were clamped with greater force than specified, which could result in improper gap verification and shimming. Boeing identified the problem in February and announced it on Tuesday.

The Federal Aviation Administration (FAA) said it “is investigating manufacturing flaws affecting certain Boeing 787 jetliners. The agency continues to engage with Boeing”.

A person briefed on the matter said the horizontal stabiliser issue could require the inspection of as many as about 900 airplanes.

Boeing said the stabiliser issue, identified at a production plant in Salt Lake City, Utah, was being corrected on airplanes not yet delivered and was not an immediate flight safety issue.

“Analysis is underway to determine if action is required on the in-service fleet,” Boeing added.

On Monday, the FAA said it was also investigating two other manufacturing flaws in some Boeing 787 Dreamliners, but said it was too early to say if it will require new inspections.

In late August, Boeing had said that airlines had removed eight 787 Dreamliners from service as a result of two distinct manufacturing issues in fuselage sections.

Boeing said on Monday some airplanes have shims that are not the proper size, and some airplanes have areas that do not meet skin flatness specifications. Boeing identified the shimming issue in August 2019. “Individually these issues, while not up to specifications, still meet limit load conditions. When combined in the same location, however, they result in a condition that does not meet limit load requirements,” Boeing said.

Boeing said it expected the inspections to affect the timing of 787 deliveries in the near term. Boeing also said it secured its first 737 MAX order in 2020, while also recording more cancellations as customers continued to ditch orders for the grounded MAX jets.