Although the upgraded Drone's strength had greatly increased, it still lacked Stealth Ability and could be detected by various radars, much to Yan Fei's regret. He could only have the Drone fly at a low altitude, skimming the sea surface and using the radar's detection blind spots to avoid being tracked. Due to this concern, he was temporarily unable to grant the Drone free flight at an altitude of thirty thousand meters.
Yan Fei continued to test the Drone's various data points. With a thought, the Drone emitted a loud sonic boom and began flying at supersonic speeds. He saw the Drone flying close to the sea surface at high speed, leaving behind a huge white line on the surface following it. The Drone, moving at three times the speed of sound, appeared a kilometer away in an instant, more than three times faster than the Level 3 Drone.