Definition
A radio frequency reserved internationally for emergency communications by aircraft and vessels in immediate danger. The two primary aviation distress frequencies are 121.5 MHz (VHF, civilian) and 243.0 MHz (UHF, military). These frequencies are continuously monitored by air traffic control facilities, search and rescue services, and many aircraft, allowing a pilot in serious trouble to call for help and be heard quickly.
Plain English
A special radio channel set aside worldwide for pilots and others to call for help when they are in serious trouble. Help is listening on these channels around the clock.
Context Anchor
You may see this term in radio communication procedures, emergency checklists, and discussions of aircraft emergency equipment.
Derivation
From the Latin distringere, meaning to pull apart or strain — the same root as 'distress,' which came to mean severe trouble or danger. A distress frequency is, literally, the frequency you use when you are in trouble.
Why Pilots Care
It guarantees that emergency calls reach air traffic control and nearby aircraft immediately, enabling rapid rescue response.
Intuition Check
Frequency does not mean “how often” here. It means the radio channel. Distress does not mean mild trouble here. It means a serious emergency where immediate help may be needed.
Example Sentence 1
After losing contact with the tower, the pilot tuned the radio to 121.5 MHz, the distress frequency, and declared an emergency.
Example Sentence 2
Controllers continuously monitor the distress frequency for any emergency transmissions from aircraft.