Air navigation is a bit out of my league. But applying critical thinking, with a long experience in surface navigation; I'll make an educated guess.
Air navigation rules, much like her older sister, surface navigation rules; are for safety and apply for all military, commercial, and civilian users of USA air space. Chances are the US DOT has them on-line. Rules logically include assigned ATC radio frequencies, transponder use, navigation lights and traffic separation schemes, such as specific altitudes for direction traveled. On the night of 9/11, the only aircraft over Chicago where the military types, with functional navigation lights.
From my experience with radar, transponders paint a significant picture on radar. The 9/11 hijackers secured transponders, which made it very difficult for ATC'ers to follow four relatively huge radar blips.
For your information, military jets do not need to wrap themselves in "tinfoil" to avoid being seen on radar. First of all, they can set their transponders to where they don't respond to civilian transponder interrogation. Secondly, they carry electronic countermeasures that allow them to evade detection on military radar. Civilian radar is much less sophisticated than military radar, accordingly, is much easier to fool.
Air navigation rules, much like her older sister, surface navigation rules; are for safety and apply for all military, commercial, and civilian users of USA air space.
Under ordinary conditions, true. Not true when an aircraft is on a combat mission under wartime rules. I'd say that morning of September 11, 2001, our fighter aircraft guarding Washington DC were operating under wartime rules.
Chances are the US DOT has them on-line. Rules logically include assigned ATC radio frequencies, transponder use, navigation lights and traffic separation schemes, such as specific altitudes for direction traveled. On the night of 9/11, the only aircraft over Chicago where the military types, with functional navigation lights.
Once we were no longer under attack, I'm sure the rules reverted back to normal.
From my experience with radar, transponders paint a significant picture on radar. The 9/11 hijackers secured transponders, which made it very difficult for ATC'ers to follow four relatively huge radar blips.
Commercial airliners carry a transponder which identifies their altitude, airspeed, and identifying information. Military aircraft are equipped with transponders that function that way in normal conditions, but in a combat mode, they operate in a different mode using classified frequencies. They would not show up on civilian radar.