At airports with an ATC tower in operation, clearances may be received from either ground control or a specific clearance delivery frequency when available. At airports without a tower or FSS on the field, or in an outlying area, clearances may be received over the radio through an RCO (Remote Communication Outlet) or, in some cases, over the telephone. In certain areas, a clearance delivery frequency is available that is usable at different airports within a particular geographic area—for example, class B airspace. If the above methods are not available, your clearance can be obtained from a ARTCC once you are airborne, provided you remain VFR in Class E airspace. The procedure may vary due to geographical features, weather conditions, and the complexity of the ATC system. If in doubt, pilots should ask the nearest FSS for the most appropriate means of obtaining their IFR clearance. A clearance issued prior to departure will normally authorize flight to the airport of intended landing. Sometimes a short-range clearance is issued to a fix within or just outside of the terminal area, and pilots are advised of the frequency on which they will receive the long-range clearance direct from the center controller.

An IFR clearance will contain the following items:

1. Clearance Limit (destination airport or fix)

2. Route (initial heading)

3. Altitude (initial altitude)

4. Frequency (departure)

5. Transponder (squawk code)

Cleared As Filed 

ATC will sometimes issue an abbreviated IFR clearance based on the route of flight as filed in the IFR flight plan provided the filed route can be approved with little or no revision.

Clearance Void Time

When operating from an airport without a tower, a pilot may receive a clearance containing a provision that if the flight has not departed by a specific time, the clearance is void. A pilot who does not depart prior to the clearance void time must advise ATC as soon as possible of his/her intentions. ATC will normally notify the pilot of the time allotted to notify ATC. This time cannot exceed 30 minutes.

Hold for Release

ATC may issue hold for release instructions in an IFR clearance to delay an aircraft's departure for traffic management reasons (weather, traffic volume, etc.). A pilot may not depart utilizing that IFR clearance until a release time or additional instructions are received from ATC.