Definition
An ATC instruction directing a pilot to listen on a specified frequency without initiating a call to the controller. The pilot tunes the new frequency and stands by for the controller to call them; no check-in transmission is required unless specifically requested.
Plain English
When a controller tells you to monitor a frequency, just tune it in and listen. Do not call the controller to announce that you are there. They will call you if they need to.
Context Anchor
Heard in ATC radio instructions, often when switching from ground control to tower, tower to ground, or from one controller to another.
Derivation
From the Latin monere, meaning to warn or remind, which gave rise to monitor as someone or something that watches or listens attentively. In radio use, to monitor a frequency means to keep an ear on it without actively transmitting.
Why Pilots Care
Keeps the pilot aware of traffic calls, updated instructions, and potential conflicts while keeping the channel clear.
Intuition Check
Monitor does not mean casually keep an eye on something here. In radio communication, it means tune the named frequency, listen, and wait; it does not automatically mean make a radio call.
Example Sentence 1
Approach instructed the pilot to monitor tower on 118.3, so the pilot tuned the frequency and waited rather than checking in.
Example Sentence 2
After the handoff, the pilot monitored approach control for sequencing instructions.