In the Arabian Gulf, Iran's drones pose rising threat to US vessels

High above the Arabian Gulf, an Iranian drone crosses the path of American fighter jets lining up to land on the USS Nimitz.
The drone buzzes across the sky at least a mile above the massive aircraft carrier and is spotted by the fighters. It is unarmed.
But for the senior Navy commanders on the ship, the presence of the enemy drone so close is worrying. Their biggest fear is the surveillance aircraft will start carrying weapons, posing a more direct threat to US vessels transiting one of the world's most significant strategic and economic international waterways. 
"It's just a matter of time before we see that," said Navy Rear Adm. Bill Byrne, commander of the carrier strike group that includes the Nimitz. He said the Iranian drone activity has "generated a lot of discussion" and was becoming an increasingly pressing matter of concern. 
If, at some point, Byrne believes a drone is threatening his ship, he and his staff would have to carefully proceed through the required responses - efforts at communication, sounding the horn, firing flares and warning shots, and flying a helicopter close to the unmanned vehicle. If all those efforts fail and he still perceives a threat, Byrne said it would be his duty, his "responsibility," to shoot down the Iranian drone. 
So far, it hasn't come to that. But the drones have become an even more dangerous security risk as US carriers in the Arabian Gulf like the Nimitz play a key role in Iraq and Syria. Planes from these ships are regularly flying to each country to bomb Daesh terrorists and other targets. From the Nimitz alone, US fighter jets flew missions resulting in at least 350 bombs being dropped on Daesh just in the last month. 
Iran has routinely challenged US ships and aircraft across the Gulf, asserting at times that the entire waterway is its territory. Navy commanders say Iran's unpredictable behavior is the biggest safety hazard. 
"Iranians don't always follow the rules," Byrne said. "There is a well-established set of norms, standards and laws. They don't tend to follow them."
To counter the threat, Pentagon experts are searching for new ways to deter, defeat or disable the drones. According to Byrne and Cdr. Dave Kurtz, the Nimitz's executive officer, Iranian drones fly over the carrier strike group almost daily. 
They said the danger is that as the F/A-18 fighters return from their missions in Iraq and Syria, they circle overhead, lining up for their turn to land on the carrier. Even if the Iranian drones are only meant to annoy, their buzzing across the American flight paths risks an accident. 
Up in the carrier's control room, a book on Iranian naval and maritime forces sits above the radar screen. Commanders on the ship announce when a drone appears. Then, they go through a careful, planned response of attempted radio calls and warnings.