The military cargo aircraft, hired by the US, that intruded into Indian airspace and was forced to land at the Mumbai airport on Friday was permitted to take off on Saturday. It took off around 10.40 pm. Meanwhile, it has now been established that the aircraft was crossing over Indian territory with dual call signs — one civil and one military — which is why it was intercepted and grounded.

The aircraft had returned to its bay at the Mumbai airport on Saturday evening after it missed its slot for takeoff allocated by the ATC. An official said the pushback instruction for takeoff was given to the aircraft at 5.57 pm and the aircraft was bound to be airborne in another 20-25 minutes when slot problems arose with the Kandahar airport.

Call signs, in layman terminology, are unique designations or names with which aircraft are identified. Usually, they are unique numbers preceded by an airline’s IATA code. All non-scheduled aircraft of foreign origin or which is on military duty require prior permission, known as Air Operations Routine (AOR) number, from the Air Force headquarters. In this case, the aircraft did not have the requisite permission from the IAF.

Similarly, prior to entering Indian airspace, all civil aircraft need to obtain the DGCA clearance and obtain a YA number — also called Yankee Alfa number. The US aircraft (registration number AH 124 100), according to officials, had the DGCA clearance prior to entering Indian airspace. However, the goof-up occurred when its pilot used a US military call sign instead of the civilian one that was noted by the authorities.

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