U.S. warships in the Persian Gulf now expect regular flyovers from Iranian drones, as well as Iranian monitoring from small watercraft. While ships are equipped with expensive high-tech equipment to provide early warning alerts, it can be difficult to find out whether or not an approaching drone is armed. Systems must also monitor land-based threats, meaning that ship detection systems are multilayered and extremely complex. Commanders have highlighted that while the monitoring capabilities are not a problem, the number of threats they monitor and the human attention they require creates capacity issues.

Source: Iranian Drone Overflights of U.S. Warships in Persian Gulf Now Common – USNI News