"Our assessment, based upon the information that we have available to us, is that this incident is not terrorism-related," Detective Chief Superintendent Jason Tingley said in a statement.
"In addition to the searches that are taking place on and around the airfield, we are deploying a number of tactical options to detect and counter these drone activities and bring this to a safe conclusion. Extra officers have been brought in to support the operation," Tingley pointed out.
The airport has suspended all the flights late on Wednesday amid reports that two drones were flying over its runway.
The Sussex Police said on Thursday that it considered the recent flying of drones over London Gatwick Airport's runway as a "deliberate act."