Definition
ACT is a NOTAM and aeronautical-publication contraction used to indicate that something is active, has been activated, or is in a state of activity. It typically appears alongside another item — such as a restricted area, military operations area, runway, navigation aid, or procedure — to communicate that the referenced facility, airspace, or service is currently in operation.
Plain English
ACT is shorthand meaning the thing being talked about is turned on, in use, or operating right now.
Context Anchor
Seen in NOTAMs, FAA abbreviation lists, and short aviation notices where space is limited.
Derivation
From the Latin actus, meaning 'a doing' or 'something being done.' The shortened form ACT keeps that core sense — something is currently in action.
Why Pilots Care
Pilots must confirm a runway or aid is ACT before relying on it for takeoff, landing, or navigation.
Intuition Check
Do not read ACT as the everyday verb “to act.” In this FAA notice context, it is a short form for active, activated, or activity.
Example Sentence 1
The NOTAM showed restricted area R-2305 was ACT from 0800 to 1600 local, so the pilot planned a route around it.
Example Sentence 2
Check the current airport status to confirm which taxiways remain ACT during construction.