For distress communications, what frequency should en route aircraft maintain a listening watch on?

Maintaining a listening watch on 121.5 MHz is crucial for distress communications as it is the internationally recognized emergency frequency. This frequency is monitored by air traffic control, other aircraft, and is accessible by search and rescue organizations. It provides a common channel for distress calls, enabling pilots in emergency situations to communicate with anyone who may be able to assist them.

The frequency 121.5 MHz is designated specifically for emergency purposes, ensuring that if an aircraft encounters trouble, it has a dedicated channel to alert others in the vicinity or to signal for help. This is why keeping a listening watch on this frequency is a standard protocol for en route aircraft, enhancing safety and the chances of receiving prompt assistance during an emergency situation.