Text I

The air traffic control system is a vast network of

people and equipment that ensures the safe operation of

commercial and private aircraft. Air traffic controllers

coordinate the movement of air traffic to make certain that

5 planes stay a safe distance apart. Their immediate concern

is safety, but controllers also must direct planes efficiently

to minimize delays. Some regulate airport traffic through

designated airspaces; others regulate airport arrivals and

departures.

10 Although airport tower controllers (or terminal

controllers) watch over all planes traveling through the

airport’s airspace, their main responsibility is to organize

the flow of aircraft into and out of the airport. Relying on

radar and visual observation, they closely monitor each

15 plane to ensure a safe distance between all aircraft and to

guide pilots between the hangar or ramp and the end of

the airport’s airspace. In addition, controllers keep pilots

informed about changes in weather conditions such as

wind shear, a sudden change in the velocity or direction of

20 the wind that can cause the pilot to lose control of the

aircraft.

During arrival or departure, several controllers direct

each plane. As a plane approaches an airport, the pilot

radios ahead to inform the terminal of the plane’s presence.

25 The controller in the radar room, just beneath the control

tower, has a copy of the plane’s flight plan and already

has observed the plane on radar. If the path is clear, the

controller directs the pilot to a runway; if the airport is

busy, the plane is fitted into a traffic pattern with other

30 aircraft waiting to land. As the plane nears the runway,

the pilot is asked to contact the tower. There, another

controller, who also is watching the plane on radar,

monitors the aircraft the last mile or so to the runway,

delaying any departures that would interfere with the plane’s

35 landing. Once the plane has landed, a ground controller

in the tower directs it along the taxiways to its assigned

gate. The ground controller usually works entirely by sight,

but may use radar if visibility is very poor.

The radar controller, who is the senior team member,

40 observes the planes in the team’s airspace on radar and

communicates with the pilots when necessary. Radar

controllers warn pilots about nearby planes, bad weather

conditions, and other potential hazards. As the flight

progresses, the team responsible for the aircraft notifies

45 the next team in charge of the airspace ahead. Through

team coordination, the plane arrives safely at its

destination.

Adapted from http://stats.bls.gov/oco/ocos108.htm

The main purpose of Paragraph 2 is to: