Change of gauge (aviation)
In air transport, a change of gauge for a passenger or cargo flight is a change of aircraft that retains the same flight number. The term is borrowed from the rail transport practice of gauge change. When a feeder flight connects to a flight on a larger aircraft, this is sometimes called a funnel flight. A Y-type change of gauge is one a given flight being transferred into two other flights with different destinations and has two flight numbers. For example, flight number 100 may fly Boston-Paris-Athens, and flight number 200 may fly  Boston–Paris–Rome, with the Boston–Paris leg being on the same aircraft in both cases. Some passengers, such as persons with disabilities or who otherwise are not disposed to make a connection, prefer to book on flights without a change of aircraft. However, passengers could incorrectly assume that if they are traveling on a single flight number they will not be required to change planes. Single flight numbers are typically used for an originating domestic to international destination or the return (e.g., San Francisco to Chicago to Paris). United States. , 6 US airlines (American Airlines, Continental Airlines, Delta Air  Lines, Northwest Airlines, US Airways, and United Airlines) had flights that had a change of gauge. Title 14 CFR Part 258, "Disclosure of Change of Gauge Services," requires air carriers to disclose to passengers, travelling on a single flight number, if they will be required to change planes during the flight. Part 258 requires the air carriers to inform the consumer that there is a change of gauge in the itinerary before the reservation is made.