Boeing on Thursday warned of reduced 737 Max production and deliveries in the near term due to a parts issue originating with a supplier, Spirit AeroSystems.

“This is not an immediate safety of flight issue and the in-service fleet can continue operating safely. However, the issue will likely affect a significant number of undelivered 737 MAX airplanes, both in production and in storage,” the manufacturer said in a statement.

Shares of Boeing fell 3% in after-hours trading on Thursday. Shares of Spirit AeroSystems fell 4%.

Spirit manufacturers aft fuselages used in Boeing jets and said in a statement it notified Boeing of a “quality issue” with certain 737 models.

“Spirit is working to develop an inspection and repair for the affected fuselages. We continue to coordinate closely with our customer to resolve this matter and minimize impacts while maintaining our focus on safety,” the company said.

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