Two separate collisions were narrowly avoided at Auckland International Airport after pilots were erroneously given clearance to use a runway another planes were already using.
The first incident occurred on May 29 last year when a Saab SF340A aircraft was given clearance to line up for takeoff infront of a landing Raytheon 1900D.
The pilots of both planes took action to avoid a collision.
The Civil Aviation Authority (CAA) investigation found the incident occurred because the aerodrome controller mistook the call sign of the aircraft she intended to line up for take-off on another runway.
"(She) thereby inadvertently instructed another aircraft to line up in front of the aircraft that was landing."
On August 1 last year a Raytheon 1900D mistakenly accepted the take-off clearance of another Raytheon 1900D which had a similar call sign.
The pilots again managed to avert a collision and stop on the runway without any damage.
The CAA found the aerodrome controller was distracted by deteriorating weather conditions and the pilots of one plane mistook their clearance signal for that of another aircraft.
However, the CAA said the aerodrome controller contributed to the mistake by not using phonetic pronunciation and issuing the clearance too quickly.
"Had the aerodrome controller attended fully to the read-back, he would probably have reacted to the crossed transmission and might have prevented the runway incursion."
Different air traffic controllers and pilots were involved in the two incidents.
In both cases the people involved were fully qualified and had passed proficiency checks.
The CAA made several safety recommendations including on the conditions for the use of multiple and angled taxiways for runway entry, situational awareness in the runway environment, the recording and investigation of runway incidents and the issues and acceptance of conditional clearances.
