Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. A sky marshal (also known as air marshal or flight marshal) is an undercover law enforcement or counter terrorist agent on board a commercial aircraft to counter aircraft hijackings. Sky marshals may be provided by airlines such as El Al (who provide sky marshals on every flight), or by government agencies such as the Royal Canadian Mounted Police, German Federal Police, US Federal Air Marshal Service or the United Kingdom Metropolitan Police.The Canadian Air Carrier Protection/Protective Program (CACPP) began on September 17, 2002 when a Memorandum of Understanding was signed between the Royal Canadian Mounted Police with Transport Canada, the authority responsible for Canadian aviation security, and the Canadian Air Transport Security Authority (CATSA), for the implementation and administration of the CACPP.