If you discover that you are unable to talk to air traffic control, a number of possibilities may exist. Depending on your altitude and frequency coverage, you may have flown into a dead area where no communications are possible with air traffic control. You might be inside the controller’s frequency coverage, but near the edge of it. In this case, you might be able to hear air traffic control, but they can’t hear you, or vice versa.

In the right conditions, such as flying through a cloud of ice crystals, significant static can be generated. This can result in lights outside the aircraft called St. Elmo's fire. Such lights are often purple or pink and move around just in front of the windshield. A forward facing cone may also extend from sharp points on the airplane, such as the airplane's nose or wingtip fuel tanks. Whether St. Elmo's fire is visible or not, this kind of static can interfere with navigation and communication signal coverage. If you are flying along and all of a sudden you hear loud static across all your radios, this is probably the case. These conditions normally don't last more than a few minutes. Make sure your autopilot, or yourself for that matter, is not following an erroneous navigation signal.

You should check your audio system configuration. Maybe you deselected the transmitter or are transmitting on your second radio. If your having trouble hearing air traffic control, try disabling the squelch on the radio to listen for weak transmissions.

You could also try other ATC frequencies in range, such as adjacent center frequencies or nearby towers. The tower you contact can then determine what frequency you should try or obtain an explanation for the communications problems.

If everything else has failed, you can also attempt to contact air traffic control on 121.5 to ask for instructions for reestablishing radio communications. While not all air traffic facilities monitor 121.5, many airline and corporate aircraft do. So, you may be answered by air traffic control or some high altitude aircraft. Whoever you get hold of can then forward your location to air traffic control and reply with their instructions.

If the controller can’t hear your replies, the transponder may be used as a communications device. For example, “Cessna seven zero eight golf lima, if you can hear me ident.”

Maybe there is a problem with the air traffic control end of things, such as a fire at the transmitter site or another pilot with a stuck mic, who is blocking the frequency.

Regardless of the reason, the FAR’s spell out exactly what we should do while we troubleshoot the problem and try to reestablish communications. Air traffic control will base their actions on the expectation that we will comply with this regulation. The rule first states that if we encounter VFR conditions at any point during the failure, that we should continue the flight under VFR and land as soon as practicable.