Flights out of Wellington were cleared for take-off yesterday, after nearly a week of disruptions caused by persistent heavy fog.

Passenger backlogs from last night were also cleared as airport staff gave a cautious welcome to a lift in low cloud and fog.

The conditions were caused by humid warm air from the subtropics condensing as it moved over cold seas around Wellington.

A MetService forecaster said the fog was expected to completely clear early today.

Spokesmen for Air New Zealand and Qantas reported some delays yesterday but said aircraft had returned to scheduled timetables.