A couple in flight gun issues that I found looking for the one that Jay mentioned. There are several incidents with guns past security but I only was looking for ones when they got on board
[FONT=arial, helvetica, sans-serif]McCarran Int'l Airport, Las Vegas[/FONT] [FONT=arial, helvetica, sans-serif]TSA said it was investigating a pilot's report that his gun was missing. The pilot, who was trained to carry a gun in the cockpit, had been traveling as a passenger. During that flight, the gun was placed in a lockbox and stored in the plane's cargo section. When the pilot arrived in Las Vegas, the lockbox could not be found. [FONT=verdana, arial, sans-serif][February 2004]
Source: The Washington Post[/FONT] [/FONT]
The one below is a STUN gun not a 'bullet' gun.
[FONT=arial, helvetica, sans-serif]LaGuardia Airport, New York[/FONT] [FONT=arial, helvetica, sans-serif]A woman reportedly passed through security with a stun gun and knife. The woman, traveling to Denver, said she discovered the items during the flight and notified a flight attendant. The pilot alerted officials in Denver, where police met the plane and took the woman into custody for questioning. She was released without charge. [FONT=verdana, arial, sans-serif][December 2003 or January 2004]
Source: Airline Industry Information (trade publication), New York Daily News[/FONT]
[/FONT]http://seattletimes.nwsource.com/news/nation-world/airportinsecurity/breaches/