Air Traffic Control (ATC) clearances are issued solely for the purpose of preventing collision between aircraft. Whether operating VFR or IFR, a pilot must not deviate from the air traffic clearance without obtaining an amended clearance. If the pilot cannot comply with any provision of the clearance, ATC should be informed immediately giving a brief reason, and normally ATC will issue an amended clearance. In the event of emergency deviation from the provisions of an ATC clearance, the pilot must notify ATC as soon as possible and get an amended clearance.
Understanding and complying with air traffic clearances also speeds up traffic movement on an airport. Before starting to taxi, the pilot should always call for a taxi clearance from the tower. (At many airports, this is done on a special radio frequency assigned to Ground Control.) Then, when cleared to a particular runway, the pilot may taxi close to but not onto the specified runway. A clearance to move onto the runway, and to take off, must be obtained on the regular control tower frequency.
When giving takeoff or landing instructions, if a tower controller cautions the pilot about "wake turbulence," it is a warning that turbulence may exist behind another aircraft that has just made a takeoff or landing. After receiving such an advisory, the pilot should analyze the situation and determine the proper course of action. Even though a takeoff or landing clearance has been issued, it may be safer to wait or to change the intended operation in some way. In that case, the pilot should ask the controller for a revised clearance. "Cleared for takeoff" or "Cleared to land" means only that the runway is or will be clear for the takeoff or landing.
Sometimes clearances include the word "immediate," such as "Cleared for immediate takeoff." Such communications are to be interpreted as meaning that if the pilot takes off at once there will be adequate separation from other aircraft. It is not an order to go. The controller cannot be expected to do the pilot's thinking. If there is any reason to believe the takeoff or landing cannot proceed safely, it is the pilot's responsibility to decline the clearance. The controller's primary job is to aid in preventing collisions between aircraft, not to advise pilots on flight procedures.
The FAA desires to help the student pilot in acquiring sufficient practical experience in the operating environment. To receive additional assistance while operating in areas of concentrated air traffic, a student pilot need only identify oneself as a student pilot during the initial call to an FAA radio facility. For instance, "Dayton Tower, this is Fleetwing 1234, Student Pilot, over." This special identification will alert FAA air traffic control personnel and enable them to provide the student pilot with such extra assistance and consideration as may be needed. This procedure, however, is not mandatory.