[Moose4]

Those planes have a transponder on them, and when they are issued their clearance to depart, they're issued a four-digit code from 0000 to 7777 called a "squawk" code. The crew dial the code into the transponder. Air traffic controllers then use the specific code from the transponder to identify that particular aircraft. (The transponder replies to the radar signal from the ground, and sends the code, the plane's altitude and airspeed and other info back to the ground, and that's displayed on the controllers' screens.) There are three specific codes that never get randomly assigned, and are always treated seriously:

7500 - hijack
7600 - radio failure
7700 - inflight emergency

I don't know if there's others or not, or if there's a single button they can push to instantly squawk 7500 or 7700. I'm just a plane geek, not a real pilot (sadly).

}:-)4

[NautiNurse]

thanks for the info

[expatpat]

I'm a pilot, and your explanation is a good one, but there may be a one-button activation of the 7500 code, as you suggest. I don't know, I'm not Air Transport.

[RckyRaCoCo]

7500 - hijack 7600 - radio failure 7700 - inflight emergency

I don't know if there's others or not..

7007.....spy onboard?