After the September 11 attacks, there was an immediate call to action regarding the state of aviation security measures as the hijackers involved in 9/11 were able to successfully pass through security and take command of the plane. The existing security measures flagged more than half of the 19 hijackers in 9/11; however, they were cleared to board the plane because their bags were not found to contain any explosives. In the months and years following September 11, 2001, security at many airports worldwide were reformed to deter similar terrorist plots. Changes in airport security Prior to September 11, 2001, airport screening was provided in the U.S. by private security companies contracted by the airline or airport. In November 2001, the Transportation Security Administration (TSA) was introduced to take over all of the security functions of the country's airports. The TSA increased the number security agents employed from 16,200 to 56,000 and increased their compensation. In addition, they reformed the training for these agents. Prior to 9/11, the security staff was generally undertrained with a reported training time of 12 hours prior to 9/11; afterwards, this training was increased to more than 100 hours. They also implemented verification tests of the training by projecting images of banned objects on machines to see if workers would be able to identify them. The actual process of security screening was revised as well after 9/11. Passenger pre-checks became standard and the percent of baggage screened for explosives increased from an approximate 5% to 100%. In some countries, for example, Sweden, Norway, and Finland, there were no or only random security checks for domestic flights in 2001 and before. On or quickly after September 11, decisions were made to introduce full security checks there. It was immediately implemented where possible, but took one to two years to implement everywhere since terminals were often not prepared with room for it. The TSA also introduced changes on the airplanes themselves, including bulletproof and locked cockpit doors and air marshals which became standard on commercial passenger aircraft. Increased security on aircraft Cockpit doors on many aircraft are reinforced and bulletproof to prevent unauthorized access. Passengers are now prohibited from entering the cockpit during flight. Some aircraft are also equipped with CCTV cameras, so the pilots can monitor cabin activity. Pilots are now allowed to carry firearms, but they must be trained and licensed. In the U.S., more