In the hours before the attack on the two tankers in the Gulf of Oman on Thursday, the Iranians spotted a US drone flying overhead and launched a surface-to-air missile at the unmanned aircraft, a US official told CNN. The missile missed the drone and fell into the water, the official said. Prior to taking fire, the American MQ-9 drone observed Iranian vessels closing in on the tankers, the official added, though the source did not say whether the unmanned aircraft saw the boats conducting an actual attack.