>>4396736 lb
Civilian drones need batteries.
They are not civilian drones. Only military drones could stay up that long and pose a threat.
Airport and port security: Abu Dhabi and Gatwick were the first in line to deploy drones in order to ensure on-site safety. In Gatwick, “Skyranger” drones equipped with high-definition cameras take snapshots and forward them to officers using portable consoles up to half a kilometer away. In Abu Dhabi, drone cameras are being used to assess and monitor accidents, to provide information during search and rescue situations, and to gather information about approaching vessels or ships with sensitive cargos.
https://www.dw.com/en/a-guide-to-military-drones/a-39441185
https://assolution.com/blog/drones-and-corporate-security-the-future-is-now/