on duty

Idioms  

1. At one's post, at work, as in The new nurse was on duty that evening, or The watchman was fired because he was drunk on duty. [Mid-1600s] The antonym, off duty, means “not engaged in one's work,” as in Captain Smith was much more amiable when he was off duty. [Mid-1800s]

---

Example Sentences

Rocket launches can be impacted by different 'weather rules' which need to be met before the launch weather officer on duty can give the 'go' decision on weather.

From BBC • Mar. 30, 2026

National Transportation Safety Board Chair Jennifer Homendy said the inquiry was ongoing and would include interviews with the two controllers on duty on Sunday night.

From BBC • Mar. 24, 2026

About 15 minutes after the collision, the controller is still on duty, radioing to a Frontier pilot lined up for the same runway.

From The Wall Street Journal • Mar. 24, 2026

The accused include the station master on duty on the night of the accident, other railway officials and two Italian former employees of the trains' parent company, Ferrovie dello Stato.

From Barron's • Mar. 23, 2026

I asked, but the attendant had just come on duty and knew nothing of Sass.

From "Homeless Bird" by Gloria Whelan