Fly-by-wire aircraft
   Fly-by-wire aircraft use a computerized control system that decides
   how to best control surface movements, engine fuel-flow rates, and so
   on. There is no direct connection between the pilot and the flight
   control surfaces in this kind of setup. Instead, the pilot gives
   instructions to the computer which interprets them, hopefully
   correctly. The computer is able to update the settings hundreds of
   times per second, something human pilots can't do, and in theory
   results in a more efficient, smoother, and safer flight. Some more
   recent planes are even able to land themselves. The controversy with
   such planes concerns their failure modes. If the computer conks out
   for some reason, it may not be possible for the pilot to dead-stick
   the plane in for a landing, since some of the more efficient control
   surfaces must have their parameters updated very frequently to remain
   airborn. Also, some early fly-by-wire planes may have had programming bugs
   that caused unexpected behavior. Finally, the Airbus A320, a
   fly-by-wire aircraft, has been perceived as accident-prone,
   allegedly because of the fly-by-wire system, though this has never
   been proven. Currently the only fly-by-wire commercial airplanes
   are the Airbus A320 and A340, with the A319, A321, A330, the Boeing
   777 and the Tupolev TU204 entering production shortly. Many
   military aircraft have been fly-by-wire for years. (For further
   discussion of fly-by-wire aircraft, see the extensive RISK archives on
   this topic.)

"Glass-cockpit" aircraft
   Such aircraft are not fly-by-wire. They display several flight
   instruments on a CRT screen in the cockpit, and have an integrated
   flight management system (sophisticated autopilots) but still have a
   direct connection between the cockpit control column and the control
   surfaces. The MD-11 and some MD-80s are examples of glass-cockpit
   planes that aren't fly-by-wire. 

Overbooking
   The airline practice of selling more tickets than there are seats
   on the aircraft. Airlines like to fly full flights, the fuller the
   better. Since on any given flight there are likely to be one or two
   no-shows, the airlines tend to oversell the flight to compensate.
   If more people show up than there are seats, the airline will first
   ask for passengers to voluntarily give up their seats in exchange
   for an incentive of the airline's choosing (e.g., typically a free
   round trip ticket), and then if there aren't enough volunteers, the
   airline will involuntarily bump some of the passengers. DOT rules
   specify how the airlines must compensate involuntarily bumped passengers.

Blackout
   Days during which a special fare does not apply. Usually days with
   heavy traffic, such as the day right before a holiday.

DOT
   US Department of Transportation

Codes
   Every scheduled airline has a two character code, and most also
   have a three-character code. For example, United Airlines is UA,
   USAir is US, and Southwest is WN. Most charter airlines have two-
   character codes, and some have three-character codes. Some airlines
   share their two-character codes, and some airlines have more than one code.
   Airports have three-character designations, with BOS for Boston, PIT for
   Pittsburgh, and EWR for Newark, among others.

Code-sharing
   Some airlines have "code-sharing" agreements with other airlines,
   in which each airline may list flights on the other airline
   under their own "code". Thus, when consumers purchase tickets from
   an airline, the actual flight (or some segments of the flight) may
   be on an entirely different carrier. These agreements typically
   arise as special arrangements linking the routes of a US airline
   with a foreign carrier. For example, United Airlines and Lufthansa,
   USAir and British Airways, American Airlines and South Africa
   Airways, etc. Travel on code-share flights is eligible for frequent
   flyer miles on either airline.

ARC
   Airline Reporting Company. A travel agency must be ARC approved
   before it can issue tickets. When a customer pays a travel agent
   for tickets, the travel agent sends the money to the ARC, which
   acts as a clearinghouse for the airlines.