All Air New Zealand planes cleared to fly following lightning

Air New Zealand says all planes inspected following lightning in the upper North Island on Tuesday were cleared to fly that day.

A number of aircraft were inspected by engineers as a precautionary measure as a result of the storm.

The airline said on Tuesday a number of departures were delayed or cancelled as a result of several aircraft requiring inspections due to possible lightning strikes.

More engineers were deployed to carry out the checks as quickly as possible.

During lightning storms, ground staff who load and unload aircraft are required to stop activity on the tarmac and this exacerbated the problem.

Air New Zealand chief operational integrity standards officer Captain David Morgan said while aircraft were insulated and designed to withstand any lightning strikes, they must be inspected before they can depart.

There was significant flow-on disruption across the airline's domestic network throughout the day.

Lightning easily passes through aircraft, the majority of which are still made of aluminium, a good conductor of electricity.

When lightning strikes a plane, it sends electricity into the plane's skin which follows the outer surface of the plane's frame and then back into the air, through small antenna-like devices called static wicks on the trailing edges of wings.

Aircraft largely built of carbon fibre such as Boeing 787 Dreamliners and Airbus A350s have copper mesh embedded in them to conduct lightning.

Avionics and fuel tanks are specially insulated against lightning strikes.