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A "close call" by two passenger aircraft over Queenstown's Lake Wakatipu is being investigated by the Civil Aviation Authority (CAA).

The two planes came close enough to spark an automatic warning to the two pilots, the Otago Daily Times reported.

CAA spokeswoman Emma Peel said yesterday an Air New Zealand Boeing 737 was approaching Queenstown Airport's runway last Saturday when it was warned by its "terrain collision avoidance system" another aircraft was in the area.

The pilot did a "standard" turn, to ensure he could see the other plane, a Glenorchy Air light aircraft, before landing.

"There was no risk of collision. The pilots could see each other. They were both in controlled airspace," Ms Peel said.

Queenstown's Air Traffic Control unit notified the CAA about the warning.

Mr Peel said the CAA would review reports from Air Traffic Control, Glenorchy Air and Air New Zealand about the incident and decide whether any further action was needed.

Transport Accident Investigation Commission spokesman Ken Mathews said the commission had been notified about the "lowest level" warning incident and had decided not to investigate.