Originally Posted by
CitizenTerrorist
It's exceedingly rare to have a complete loss of comms on a modern commercial aircraft. It's going to have at least 2 independent comm radios.
In the rare case of loss of comms, one can signal that loss to ATC by going to a special transponder code at which point one is to continue to one's destination via a somewhat complicated set of criteria.
In the event of lost comms, ATC will usually attempt to contact the aircraft in question on the assigned frequency, the last assigned frequency or guard. There are a whole plethora of other frequencies they could try as well (company, UNICOM, MULTICOM, ARINC, air-to-air, etc).
Things get a little weird in DC, though. Air carriers may have different procedures they are to follow in the event of lost comms in the DC area.
This is covered by the company manual, the AIM (Airman's Information Manual, Federal Aviation Regulations (14 CFR 91.185), and is correct.
I have been in a lost communication situation when one Center sector controller forgot to hand me off, but being a regular on that route, noticed this and switched to the next frequency and queried the new sector controller, as I was out of range of the previous site. I was probably much more than 15 minutes of no-radio before I realized the problem. It was a non-event. This was pre-9/11 and a long ways from DC and its ever popular FRZ.
The rules are as described by others above. Fly the present clearance and expect further clearance instructions and attempt to re-establish communications. But you have to realize you've lost comm too.
In addition, in remote areas where comm coverage is weak or lacking, aircraft are occasionally asked to call up others on last assigned frequency or emergency frequencies to try to re-establish comm.
Most of us, especially now that SAR-SAT no longer monitors the VHF emergency frequencies try to monitor those frequencies. But, given that there are usually 2 radios and one may be busy getting weather or airport information, the other ATC, it is sometimes not possible to continuously monitor the emergency "guard" frequency.