Description

A single radio frequency is capable of handling a limited number of radio messages in a specified time. The maximum number of messages will be determined by the length of each message and its response. Ideally, a pilot should be able to transmit a message at any time of his/her choosing, and receive an immediate reply. As radio traffic increases above the ideal, the frequency becomes congested. The pilot must wait for a break in transmissions to pass a message and may have to wait for a response from the ATCO, who has to judge different priorities.

Persistent (rather than transient) frequency congestion is a frequent contributory factor in communication breakdown, usually in association with other factors.