Eight flights have been diverted from Manchester Airport due to fog, disrupting more than 1,000 passengers.
The airport's automatic landing system, which would normally take over in cases of fog, was switched off for maintenance, officials said.
The flights from Europe and Egypt were diverted to other North West and Midlands airports earlier.
Passengers were due to be driven or flown back to Manchester. Flights are now landing as usual at the airport.
An airport spokesman said: "We were doing routine maintenance on the automatic landing system as we didn't think there would be fog in August."