Southwest Airlines grounded 128 planes and canceled about 80 flights Tuesday after failing to inspect backup hydraulic systems used to control the rudder if the main system fails, the airline announced.
According to a statement by the airline, the Boeing 737-700 jets were found to have overflown a required check.
After discovering the missed inspection, the airline notified federal safety regulators and developed a plan to complete the overdue checks.
The checks will take five days to complete, Southwest said. The FAA approved a proposal to continue operating the planes as the checks are completed.
Southwest Airlines expects "very minimal impact" to Wednesday's operations, the airline said in a statement.
The Associated Press contributed to this report.