US aircraft manufacturer Boeing issued a warning on Thursday about potential new problems with its 737 MAX models, specifically a loose bolt in the rudder control system.
The US Federal Aviation Administration (FAA), has urged all operators to inspect newer models for any loss of components after an international airline reported a missing nut from a bolt during routine maintenance.
If more issues arise, the US aviation watchdog may take additional action.
The 737 MAX models had been grounded for an extended period following two accidents in rapid succession in 2018 and 2019. Boeing has since undertaken technical modifications.
Boosted by high demand, the production rate of the 737 MAX was increased earlier this year.