SEATTLE, WASHINGTON — Boeing has halted deliveries of certain 737 MAX aircraft due to a supplier quality issue involving Spirit AeroSystems, which could have originated as early as 2019, the company revealed on Thursday.

The problem is expected to impact a substantial number of undelivered 737 MAX planes, both in production and storage, possibly causing a decrease in 737 MAX deliveries in the short term.

The issue affects some models in the 737 MAX family, including the MAX 7, MAX 8, and MAX 8200, as well as the P-8 Poseidon maritime surveillance aircraft, but is not considered a safety risk, and operational planes can continue to fly. The FAA confirmed that there is no immediate safety concern based on the information provided by Boeing and will assess all affected aircraft prior to delivery.

The issue involves the improper attachment of two fittings connecting the aft fuselage, manufactured by Spirit, to the vertical tail. Some aircraft models, such as the MAX 9, have fittings from other suppliers that were installed correctly.

Boeing was officially informed of the issue by Spirit on Wednesday, but it is thought to have originated in 2019, and the number of affected aircraft is still being determined. Boeing did not comment on whether the problem would affect its plans to increase 737 production this year as it aims to deliver at least 400 MAXs in 2023. The company had planned to raise monthly MAX production rates from 31 to 38 jets by June.

Boeing stated that it had notified the FAA and is working to inspect and replace non-conforming fittings as needed. The company regrets the impact on customers and is in communication with them regarding their delivery schedules. Spirit is working on developing an inspection and repair process for the affected fuselages.

Following two fatal crashes in 2018 and 2019, the FAA has been closely monitoring Boeing aircraft. The FAA now inspects each 737 MAX and 787 plane before issuing an airworthiness certificate and approving it for delivery, a responsibility that is typically delegated to the manufacturer.