Figure 10-1 .  Flight plan form. plan to an airport without an operating control tower, the  pilot is responsible for cancelling the flight plan. This can  be done by telephone after landing if there is no operating  FSS or other means of direct communications with ATC.  When there is no FSS or air-to-ground communications are  not possible below a certain altitude, a pilot may cancel an  IFR flight plan while still airborne and able to communicate  with ATC by radio. If using this procedure, be certain the  remainder of the flight can be conducted under VFR. It is  essential that IFR flight plans be cancelled expeditiously. This  allows other IFR traffic to utilize the airspace. A pilot who files directly with the  ARTCC reports present  position and altitude, and submi ts only the flight plan  information normally relayed from  the FSS to the ARTCC.  Be aware that traffic saturation freq uently prevents ARTCC  personnel from accepting flight p lans by radio. In such  cases, a pilot is advised to contact  the nearest FSS to file  the flight plan. An IFR flight plan may be cance lled any time a pilot is  operating in VFR conditions  outside Class A airspace by  stating “cancel my IFR flight plan” t o the controller or air-to- ground station. After cancelling an  IFR flight plan, the pilot  should change to the appropriate  air-to-ground frequency,  transponder code as directed, and VFR altitude/flight level. An ATC clearance allows an aircraft to proceed under  specified traffic conditions within controlled airspace  for the purpose of providing separation between known  aircraft. A major contributor to runway incursions is lack  of communication with ATC and not understanding the  instructions that they give. The primary way the pilot and  ATC communicate is by voice. The safety and efficiency  of taxi operations at airports with operating control towers  depend on this communication loop. ATC uses standard  phraseology and require readbacks and other responses from  the pilot in order to verify that clearances and instructions  are understood. In order to complete the communication  ATC separation and information services (including radar  services, where applicable) are discontinued when an IFR  flight plan is cancelled. If VFR radar advisory service is  desired, a pilot must specifically request it. Be aware that  other procedures may apply when cancelling an IFR flight  plan within areas such as Class C or Class B airspace. When operating on an IFR flight plan to an airport with  an operating control tower, a flight plan is cancelled  automatically upon landing. If operating on an IFR flight  Clearances Cancelling IFR Flight Plans 10-3