If you are looking for military aircraft voice traffic you will find a considerable amount on the U.S. Air Force Military Affiliate Radio System (MARS) phone patch network frequencies. The primary frequencies used are 13927.1 and 20992.1 kHz. These are fun and interesting frequencies to monitor and you will be surprised at who uses this net and the traffic they pass (official and unofficial).
Frequency/Designator Matrix (USB mode)
4557.1/RK
7633.6/ACJ
13927.1/ACB (Primary)
14606.1/ACF
18617.1/Unknown
20992.6/ACZ
MARS conducts a phone patch admin net on Sundays at 1600 UTC on 13977.1 kHz (ACC).