Air traffic control is a service provided by ground-based air traffic controllers to direct aircraft on the ground and through controlled airspace, provide advisory services in non-controlled airspace, and prevent collisions while organizing and expediting the flow of air traffic. Controllers use equipment like radios, navigation aids, publications, and vehicles to direct planes safely through the different phases of flight from the airfield to approach control with standardized phraseology. Human factors and equipment help controllers manage traffic flow while preventing incidents and accidents.