May 1, 1961 -- In the first hijacking of a U.S. airliner, a Miami man takes over a National Airlines flight and demands the plane land in Cuba. After three more U.S. flights are hijacked in three months, President John F. Kennedy assembles the first cadre of 18 sky marshals, assigned at the request of the FBI or the airline.
Aug. 10, 1961 -- In a press conference, President Kennedy says of the service: "Now, let me say that we are -- have ordered today on a number of our planes a Border Patrol man who will ride on a number of our flights. We are also going to insist that every airplane lock its door, and that the door be strong enough to prevent entrance by force, and that possession of the key be held by those inside the cabin so that pressure cannot be put on the members of the crew outside to have the door opened."
1968 - 1972 -- In four years, about 75 U.S. flights are hijacked to Cuba, mainly by exiles and extortionists.
October 1970 -- U.S. Customs Service establishes a greatly expanded sky marshal program with 1,784 agents.
1974 -- The Federal Aviation Administration takes over the air marshal program; ranks dwindle significantly after X-ray screening begins at U.S. airports.
June 14, 1985 -- Brandishing grenades and guns, Hezbollah hijacks TWA Flight 847 from Athens and holds the passengers hostage for 17 days. President Reagan signs a bill to add air marshals on international flights; ranks rise to nearly 400.
Sept. 11, 2001 -- On the day of the terror attacks in New York and Washington, there are only 33 air marshals, none of whom fly domestically. The hijackings spur an overhaul of aviation security, including the hiring of more than 4,000 air marshals for the newly created Transportation Security Administration. The service is headed by Thomas Quinn, a former Secret Service agent.
Nov. 12, 2001 -- In one of the first incidents involving air marshals, a man flying from Pittsburgh to Washington is subdued after breaking a new federal rule by getting up to use the bathroom in the last 30 minutes of the flight. Passengers are told to place their hands on their heads or on the seats in front of them until the plane lands.
Summer 2002 -- Air marshals begin complaining publicly about a dress code requiring business attire, saying the dress code and other polices are blowing their cover. This begins a four-year battle between air marshals and managers before rules are relaxed.
Aug. 31, 2002 -- After detaining an unruly passenger (PDF) en route from Atlanta to Philadelphia, two air marshals hold the cabin at gunpoint. After landing, they also detain a Florida doctor of Indian descent, who sues the TSA (PDF), saying that one air marshal told him, "We didn't like the way you look." The agency settles for $50,000.
Nov. 2, 2003 -- The air marshal program moves from the TSA to Immigration and Customs Enforcement.
June 29, 2004 -- Air marshals monitor and briefly detain (PDF) 13 members of a Syrian band flying from Detroit to Los Angeles on expired visas after a series of suspicious actions in flight. After determining the men aren't a threat, they release them.
Aug. 30, 2004 -- The Department of Homeland Security inspector general releases a report (PDF) that cites numerous problems with air marshal background checks.
Oct. 16, 2005 -- The air marshal program moves back to the TSA.
Dec. 7, 2005 -- Air marshals shoot and kill a mentally ill passenger, Rigoberto Alpizar, in the jetway after he ran off a flight in Miami with his backpack and said he had a bomb. It is the first shooting (PDF) by air marshals since 9/11.
March 2006 -- Dana Brown, another Secret Service manager, replaces Quinn as director of the service.
May 25, 2006 -- The House Judiciary Committee releases a report (PDF) concluding the agencyâs dress code and other policies jeopardize the air marshalsâ undercover mission, prompting the new director to make changes.
Aug. 23, 2006 -- Three air marshals take control of a flight from Amsterdam to Mumbai, India, after witnessing 11 Indian passengers acting suspiciously, including passing out cell phones to one another. After landing, the men are determined not to be a threat and released.
June 2008 -- Robert S. Bray, the agency's third director, takes over after Brown announces his retirement.