Call signs

Each operator of a scheduled or charter flight uses an airline call sign when communicating with airports or air traffic control centers. Most of these call-signs are derived from the airline's trade name, but for reasons of history, marketing, or the need to reduce ambiguity in spoken English (so that pilots do not mistakenly make navigational decisions based on instructions issued to a different aircraft), some airlines and air forces use call-signs less obviously connected with their trading name. For example, British Airways uses a Speedbird call-sign, named after the logo of its predecessor, BOAC, while America West used Cactus reflecting that company's home in the state of Arizona and to differentiate itself from numerous other airlines using America and West in their call signs.