India, Sept. 11 -- The terrorist attacks on the World Trade Centre on September 11, 2001 significantly changed air travel and airport security in the US and the world over.

The US centralised airport security policy with the creation of the Transportation Security Administration (TSA) in November 2001. Before 9/11, airports and airlines individually used to strike deals with local private security companies but this arrangement made way for a federal agency taking over recruitment. Today, the TSA has around 65,000 employees-50,000 are responsible for direct screening of passengers and luggage.

Metal detectors and X-ray machines have been part of airport security since the 1970s. Rules and implementation for carry-on baggage were lax unt...