What is the purpose of 121.5 MHz emergency frequency?

The purpose of the 121.5 MHz emergency frequency is specifically to provide a means for pilots and other aircraft to communicate during emergencies when they may not be in contact with air traffic control (ATC). This frequency is designated internationally as the primary emergency frequency for aviation.

In crisis situations, such as technical failures, navigational problems, or life-threatening circumstances, pilots can use 121.5 MHz to signal for help or communicate their distress to nearby aircraft or ATC if they are in range. The frequency is monitored by search and rescue operations and other relevant authorities, making it crucial for ensuring the safety of aircraft in emergency situations.

Routine communications with ATC occur on different frequencies designated for that purpose, while flight plan filing is conducted through standard procedures and does not involve using 121.5 MHz. Additionally, while pilots can sometimes communicate with other aircraft, the main function of 121.5 is not for that purpose, but rather for emergencies.