Section 4. Hours of Duty


ATC must be provided during published hours of operation. Early opening or late closing may be occasionally necessary to accommodate traffic which may otherwise divert or cancel its operation because air traffic control is not available at the airport. Good judgment, based on known or observed traffic, must be exercised when deciding to extend operating hours.


Use Coordinated Universal Time (UTC) in all operational activities. The word “local” or the time zone equivalent must be used to denote local when local time is given during radio and telephone communications. When written, a time zone designator is used to indicate local time, e.g., “0205M” (Mountain). The local time may be based on the 24-hour clock system. The day begins 0000 and ends 2359. The term “ZULU” may be used to denote UTC. In general, operational forms will be recorded in UTC and administrative forms recorded in local time.

  1. Facilities without a direct coded time source must, at 8-hour intervals, obtain an accurate time check from ARTCC/s equipped with coded time source or from any one of the following standard frequency and time radio stations:
  1. WWV, Fort Collins, Colorado, on 2.5, 5, 10, 20, and 25 MHz, which broadcasts continuously except 45 to 49 minutes after each hour. The telephone number for WWV is (303) 499-7111.
  2. WWVH, Kekaha, Kauai, Hawaii, on 2.5, 5, 10, 15 and 20 MHz, which broadcasts continuously except 15 to 19 minutes after each hour.
  3. CHU, Ottawa, Canada, on 3.33, 7.34, and 14.670 MHz, which broadcasts continuously on all frequencies.
  4. U.S. Naval Observatory, Washington, D.C., telephone number (202) 762-1401.
  1. Facilities are exempt from performing time checks if they meet the following requirements:
  1. The facility clocks are digital.
  2. The clocks are tied to the direct coded time source on the multi-channel recorder, any one of the listed standard frequency and time radio stations or other time generating device.


FAA Order JO 6670.4, Maintenance of MultiChannel Recorder Equipment, Chapter 4.


Part-time facilities must establish procedures for opening and closing their facilities. The procedures must be coordinated with the facility having IFR jurisdiction and must include, as a minimum, the following:

  1. Broadcast an announcement upon resuming/terminating service on appropriate frequencies. This broadcast must include, as a minimum, a statement that indicates ATC service and the airspace class of service being resumed or terminated, e.g, “[Time] Waukesha Tower is terminating Class Delta services Class E/G Airspace now in effect.”
  2. At locations where neither a tower nor FSS continues service or the FSS does not have lighting controls/approach aid monitoring capability, do the following as appropriate:
  1. Include, in the termination broadcast, the status of the airport and essential components; e.g., Navigational Aids (NAVAIDs), airport and approach lighting, weather, NOTAMs concerning NAS, and field conditions.
  2. If there is an approach procedure for the airport, inform the facility having IFR jurisdiction of the information determined appropriate in subparagraph b1. This information need not be forwarded when the sector controller advises no arriving traffic.
  1. At the time of closure, the facility having IFR jurisdiction must inform all inbound flights with which it has communications and which will use any of the components associated with the airport of the information received from the part-time facility.
  2. If a collocated FSS operates when the tower is closed, pertinent flight data must be exchanged before the tower opens/closes.