A trend for kite fighting which sees mid air duels at up to five times the legal altitude limit is putting aircraft at risk, crash investigators have warned after a helicopter was hit.

A pilot was carrying four passenger on a sight-seeing flight over the Kent countryside when he noticed the kite and on later inspection discovered that if it had hit just inches lower it could have caused him to lose control.

The helicopter had been flying at between 700 and 1,000 feet when it was hit, more than three times the limit of the 200-feet that toys are allowed to fly at.