Why drones could not catch radar in Jammu Airforce Station?

Seven drones have been spotted in the military bases in Jammu in the last three nights. The first attack took place with two drones and the remaining five drones have been visible for the last two nights. For the first time in the country, there has been a drone attack and even after such a high alert, drones are visible repeatedly. Experts have told that why the drones could not catch the radar in the attack on the Air Force station. Watch this video.