Transport service based on published flight schedules, including extra sections.

Sometimes referred to as a center or an air route traffic control center, it houses the air traffic controllers and equipment needed to identify and direct aircraft during the en route – as opposed to the approach and departure – portion of their flights.

As defined by the National Transportation Safety Board (NTSB), an occurrence incidental to flight in which, as a result of the operation of an aircraft, any person (occupant or nonoccupant) receives fatal or serious injury, or any aircraft receives substantial damage.

The average distance one ton is carried. It is computed by dividing ton miles or ton kilometers by tons of freight originated.

A system for electronically collecting and displaying information about commercial flights and passenger reservations on them.

See unit cost.

The right to serve two or more specified points in the territory of a party to an air-transport services agreement on the same flight, provided these points are contained in the same route. If two or more separate routes are granted, the right to coterminalize points on separate routes must be specifically established.

The difference between crude oil and refined petroleum product prices, when expressed in similar units, is known as the crack spread. For example, if crude oil costs $60 per barrel and jet fuel costs $75 per barrel, the jet fuel crack spread is $15 per barrel.

A mixture of hydrocarbons that exists in the liquid phase in natural underground reservoirs and remains liquid at atmospheric pressure after passing through surface-separating facilities. The U.S. benchmark for crude-oil prices is West Texas Intermediate (WTI), measured in Cushing, Oklahoma.

The phase of flight that begins when the crew establishes the aircraft at a defined speed and predetermined constant initial altitude and proceeds in the direction of a destination. It ends with the beginning of descent for the purpose of an approach or by the crew initiating an en route climb phase.