The trailer-mounted radar is a "phased array" type - it scans the sky with a narrow beam which flicks between thousands of locations each second.

BBC: Fact file: Patriot missile defence

The Federal Air Marshal Service officially began in 1968 as the Federal Aviation Administration's Sky Marshal Program, and in the 1970s, extortion-type hijackings in the Middle East led to the deployment of some air marshals overseas.

CNN: STORY HIGHLIGHTS

The 14-year-olds also quizzed a number of journalists about their jobs, including the BBC's Dan Roan, BBC Radio 5 live's Ian Dennis and Sky Sports' Nick Collins, and got tips on what type of questions to ask.

BBC: School Report: John Terry looks to inspire new generation