As US vessels launch airstrikes against ISIS in Syria and Iraq from the USS George H. W. Bush and its strike group, Iranian surveillance drones have become a regular nuisance.

Axar.az reports citing to Sputnik an Iranian drone was first reported to have flown over a US vessel in January 2016, when an unmanned aerial spy vehicle flew over the USS Harry S. Truman and the French carrier Charles DeGaulle. The craft was determined to be of no threat after a Navy MH-60 helicopter was dispatched to investigate.

The Danish frigate Peter Willemoes, which along with other escort ships has been with the Bush and its group since January help shore up the vessel’s defenses. The carrier also has its own built-in defense systems.

The Bush’s commanding officer, Capt. Will Pennington, told Military.com, "That is a capability that the entire world is getting, and Iran is no different … These aren't small, radio-controlled drones. They're reconnaissance."

Pennington said that now Iranian UAVs are being detected almost daily, and that crewmembers employ a number of tactics to keep them at bay, saying, "We almost always have a substantial heads-up … and then we have a series of procedures that we train to that gradually, or not gradually, escalate our defensive position and our level of readiness."

Outside of an incident in March when Iranian fast-attack boats headed toward the Bush as it made its way to the Persian Gulf through the Strait of Hormuz, the encounters between US and Iranian vessels have been cordial, but Pennington and officials on board remain on alert.