[patriciaruth]

Have all of these incidents aboard airlines increased since 9/11 or are we just hearing about each and every one, now?

Decreased since 9-11. In prior years there were an average of about 70 hijackings a year of U.S. airliners, but the press went along with a policy of no publicity in order not to encourage copycats and other nut cases.

[RightWhale]

an average of about 70 hijackings a year of U.S. airliners

Can I assume this includes incidents of unruly passengers that endanger the crew, passengers, or aircraft?