When is an aircraft considered 'airborne'?

An aircraft is considered 'airborne' when it has no physical contact with the ground. This means that once the aircraft has taken off and is in flight, it is classified as airborne. The key aspect of this definition is the lack of physical interaction with the ground, which distinguishes being airborne from other states of flight operations such as taxiing or landing.

When an aircraft is taxiing, it is moving on the ground and in contact with the runway or taxiway, which clearly does not meet the criteria for being classified as airborne. Similarly, when an aircraft lands and is on the runway, it is also not airborne as it is once again in contact with the ground. Being parked at the gate implies that the aircraft is stationary and secured, thus in no way meets the definition of being airborne either.