At non-towered airports, instead of receiving instructions from an air traffic controller, aircraft pilots follow recommended operations and communications procedures for operating at an airport without a control tower. The exact procedures vary from country to country, but they may include standard arrival and departure procedures, as well as a common communications phraseology by radio transmissions over a common frequency. For example a common traffic advisory frequency is recommended for radio communication and are used in the United States, Canada, New Zealand and Australia.[3]