AIM ¶ 4-1-12 — UNICOM for ATC
AIM 4-1-12 explains when UNICOM may be used for ATC purposes — departure time revisions, takeoff/arrival reports, and relayed clearances.
UNICOM is a non-government air/ground radio service typically used at non-towered airports for advisories like wind, runway in use, and traffic. Per AIM 4-1-12, UNICOM is not a general substitute for ATC communication, but it may be used for limited ATC purposes in three specific situations:
- Revising a proposed departure time on a filed flight plan
- Reporting takeoff, arrival, or flight plan cancellation times
- Relaying an ATC clearance — but only if the ATC facility and the UNICOM licensee have made prior arrangements to handle those messages
Why this matters operationally: when departing or arriving at a non-towered field with no Flight Service outlet on the airport, UNICOM is often your only radio link to the outside world. Knowing this guidance lets you close a VFR flight plan, get a delayed clearance void time updated, or have a clearance relayed without misusing the frequency. Remember UNICOM operators are not controllers — they relay information as a courtesy, and the AIM is informational guidance rather than a regulatory mandate.
Five FAA-written-style questions. Instant explanations, every answer cites its source — no account needed.
You are flying VFR in Class E airspace at 8,500 feet MSL during the day. What are your minimum visibility and cloud clearance requirements?