There are approximately 300 Flight Service Stations located within the conterminous United States. Their normal flight service area encompasses an area within 400 miles of the station location. Although FSSs have no direct air traffic authority over either VFR or IFR traffic, they render extensive service to all air traffic. The FSSs are the backbone of the ATC Flight Information System.

 FSSs have the following functions: (1) conducting pilot preflight briefing on enroute weather and other aeronautical information pertinent to the flight, (2) providing enroute communications with pilots on VFR flights, (3) giving emergency assistance to lost VFR and IFR aircraft, (4) relaying ATC clearances, (5) originating, classifying, and disseminating notices to airmen (NOTAMs), (6) broadcasting aviation weather and national airspace information, (7) receiving and closing VFR and IFR flight plans (filed IFR flight plans are forwarded to the appropriate Center), (8) monitoring radio NAVAIDs, (9) performing initial search and rescue operations for missing VFR aircraft, (10) operating the National Weather Teletypewriter Service, (11) taking weather observations (at selected locations), (12) providing airport advisory service at non-tower or part-time tower locations, and (13) conducting the National Pilot Weather Report Program.

 Pilot Preflight Briefing. FSSs aid in fulfilling the requirements of FAR 91.5 {§ 91.5 recodified to § 91.103}, which states that the pilot will be familiar with all available information concerning the flight. A complete preflight briefing consists of: (1) a pilot weather briefing, (2) aeronautical information pertinent to the flight, and (3) flight planning assistance, at the pilot's request. You can aid the FSS preflight briefer by providing the following background information: (1) VFR, IFR, or VFR/IFR, (2) aircraft identification number, (3) aircraft type, (4) departure point, (5) estimated time of departure, (6) altitude, (7) route of flight, (8) destination, (9) estimated time enroute, and (10) estimated time of arrival.

 After the briefer has been provided this information, a preflight briefing will be given which will include:

  (1) Adverse Weather - The pilot will be advised of any weather conditions that might make it advisable to cancel or postpone the flight. Such conditions include severe thunderstorms, icing conditions, and visibility restrictions.
  (2) Synopsis - The synopsis is a brief statement which outlines the primary cause of weather conditions along the pilot's route of flight. This statement may include pressure patterns, wind flow patterns, frontal development, and frontal movement.
  (3) Current Weather - The briefer will summarize the existing weather conditions along the pilot's intended route. This may include information from Aviation Weather Reports, Pilot Weather Reports, and Radar Weather Reports.
  (4) Enroute Forecast - The briefer will give the pilot a summary of the forecast weather conditions along the proposed route. It is the responsibility of the briefer to INTERPRET and SUMMARIZE information found in Area Forecasts, Terminal Forecasts, Airmets, Sigmets, forecast amendments, and hazardous weather advisories. This information may include cloud tops, cloud layers, cloud bases, thunderstorms, strong low level wind shear at departure and destination airports, turbulence, and icing.
  (5) Destination Forecast - The pilot will be briefed on the weather that can be expected upon arrival at the destination. This information will be obtained from the Terminal Forecast (FT) and will include the portion which is pertinent to the pilot's estimated time of arrival (ETA). If a change is forecast to occur at approximately the pilot's ETA, the briefer will provide weather information to include conditions expected both before and after the change. If no Terminal Forecast is available, an interpretation from the Area Forecast will be used. This, however, will not be identified as an official forecast.
  (6) Forecast Winds and Temperatures Aloft - The briefer will provide the pilot with the average wind speed and direction forecast for the intended route. If changes are expected, the pilot will be so advised. This information will be derived from the Winds and Temperatures Aloft Forecast (FD). Temperatures aloft are not routinely given by the briefer unless (a) they are vital for flights during periods of unusually hot or cold weather, (b) an icing potential exists or, (c) they are requested by the pilot. If the pilot's planned altitude is between standard forecast wind levels, the briefer will interpolate to provide accurate wind information.
  (7) Pertinent aeronautical information, including NOTAMS.

 Notices to Airmen (NOTAMs). - A NOTAM contains information of a time-critical nature that is required for flight planning and not known sufficiently in advance to publicize through aeronautical charts or flight information publications. NOTAM information concerns the establishment, condition or change in, any component, facility, service or procedure of, or hazard in, the National Airspace System. NOTAMS are broken down into the following five categories:

  (1) Landing Area NOTAMS - include airport closure; decommissioning of a landing area; conditions which restrict or preclude the use of a runway, taxiway, or ramp; and control zone hours of operation.
  (2) Lighting Aid NOTAMs - include information related to airport light systems, approach light systems, and obstruction light outages in proximity of the airport.
  (3) Air Navigation Aid NOTAMs - include decommissioning of air navigation aids, radar failure, NAVAID restrictions, and change in hours of operation of a NAVAID.
  (4) Special Data NOTAMs - include material not covered under landing area, lighting aids, air navigation aids, or FDC NOTAMs.
  (5) FDC NOTAMs - concern compliance with Federal Aviation Regulations and are regulatory in nature. The National Flight Data Center is responsible for their collection, validation, and dissemination. FDC NOTAMs are transmitted to FSSs by teletype. These NOTAMs are NOT provided during preflight briefings unless they are specifically requested.

 When disseminated by FSSs, NOTAMs concerning the first four categories listed above are identified as follows:
  (1) NOTAM (D) - includes NOTAMs given distant dissemination (in addition to local dissemination) beyond the area of responsibility of the FSS. These include that time-critical information which would affect the pilot's decision to make a flight; for example, an airport closed, terminal radar out of service, enroute navigational aids out of service, etc. Dissemination of information in this category will include that pertaining to all navigational facilities and all IFR airports with approved instrument approach procedures. These NOTAMs are stored and repeated hourly at the end of the appropriate Surface Aviation Weather Reports until canceled.
  (2) NOTAM (L) - includes NOTAMs given local distribution via appropriate voice communications, local teletypewriter or telautograph circuits, telephone, etc. The information disseminated is primarily of an advisory or "nice-to-know" nature, that can be given to the pilot upon request on an "as-needed" basis before departure, while enroute, or prior to landing. An example of such information is, "snowbanks on the sides of the runways."

 NOTAMs which are known in sufficient time for publication and are of 7 days duration or longer are normally incorporated into NOTICES TO AIRMEN and carried there until cancellation time. FDC NOTAMS are carried in this publication and also in the NATIONAL OCEAN SURVEY APPROACH PROCEDURE CHART booklets.

 Alternate Sources of Aviation Weather and Aeronautical Information. At many locations, the number of pilots requiring preflight and in-flight weather briefings from FSSs is so great that alternative methods have been made available. After using one of these methods, you can assess the information presented and decide if you need a more detailed briefing.
 Pre-recorded Weather Announcements include: (1) TWEBs (Transcribed Weather Broadcasts), (2) PATWAS (Pilot's Automatic Telephone Weather Answering Service), and (3) AAWS (Automatic Aviation Weather Service).

 Live Weather Broadcasts include: (1) Scheduled Weather Broadcasts and (2) Unscheduled Weather Broadcasts.
 In-flight Services. FSSs are responsible for providing in-flight services for their flight service area. Having a general knowledge of an area within 400 miles of the station and a detailed knowledge of the 100 mile radius, the FSS specialist is qualified to provide in-flight services to pilots flying under IFR or VFR.

 Pilot Weather Briefing Service enables you to obtain a weather briefing for your route of flight and destination by contacting an FSS on the appropriate frequency. An enroute weather briefing follows a format which parallels that of a preflight briefing. However, you should understand that due to frequency saturation and other duties performed by the in-flight specialist, your weather briefing may not be as detailed as one you would receive by telephone or in person.

 Aeronautical Information such as current NOTAMs, preferred routes, airport data, and communications frequencies may be obtained while enroute by contacting an FSS on an appropriate frequency.

 An IFR Flight Plan may be filed in flight by contacting the nearest FSS and relaying flight plan information in the numbered sequence that it appears on the flight plan form. This will ensure the receipt of all necessary information for entry of your flight plan into the appropriate Center computer.

 Emergency Services can be provided to aircraft in distress by FSS personnel. They assist disoriented pilots through the use of VOR orientation procedures, VHF DF procedures, or a combination of both. FSSs equipped to provide DF procedures may be found in the Airport/Facility Directory.

 Air/Ground Communications may be conducted with FSSs on designated frequencies. These frequencies are associated with the FSS information boxes on sectional and enroute low altitude charts. They also appear in the Airport/Facility Directory.
 Airport/Advisory Service. Many airports without air traffic control towers or with part-time towers, have FSSs capable of providing airport advisory service to both landing and departing IFR and VFR aircraft. Airport advisory service is provided on 123.6 MHz for the area within five statute miles of an airport having no control tower but where an FSS is located. At locations where airport advisory service is provided by an FSS during the hours the control tower is closed, the local tower control frequency is used. It is recommended that pilots monitor the appropriate frequency when within fifteen miles of the airport. Refer to the AIRMAN'S INFORMATION MANUAL for services available and recommended phraseologies.

 When operating IFR at an airport having a control zone with no operating air traffic control tower and having an FSS located on the field, you may obtain an IFR flight clearance and takeoff clearance through airport advisory service. The FSS specialist will coordinate with the appropriate control facility and relay your clearance instructions.

 Enroute Flight Advisory Service (EFAS). - Weather information obtained during a preflight briefing cannot state with absolute certainty what conditions you will encounter during flight. National Weather Service forecasters can forecast the immediate meteorological future in general terms, but predicting specific time, location, and severity of weather phenomena is still not possible. Local terrain features can often affect weather patterns. Actual flight conditions can be unexpectedly different from those forecast.

 In response to the need for improved in-flight weather availability and dissemination and to provide pilot-to-briefer service of meaningful, real-time weather information, the FAA has implemented EFAS. This service is now available through a nationwide network of 44 FSSs. An EFAS facility should be contacted on 122.0 MHz by using the name of the parent FSS and the words "Flight Watch"; e.g., "Portland Flight Watch." Refer to the AIRMAN'S INFORMATION MANUAL for further details.
 Pilot Weather Report Program (PIREP). - A PIREP is another form of weather observation. No weather observation is more timely than the one you make from the cockpit of your airplane. The EFAS Flight Watch specialist uses PIREPs in accomplishing the goal of providing near real-time weather information directly to pilots in flight. The National Weather Service meteorologist uses PIREPs to update forecasts and to issue advisories; e.g., SIGMETs whenever the situation so warrants. These forecasts and advisories are, in turn, used by the FSS receiving them. They are also disseminated by teletype for use by other facilities.