In air transport, a change of gauge for a passenger or cargo flight is a change of aircraft that retains the same flight number.^[1] 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.^[2] An example of a change of gauge flight from a larger aircraft to a smaller aircraft during the early 1970s can be found in the Pan American World Airways (Pan Am) April 29, 1973 system timetable with Pan Am flight 295 from New York John F. Kennedy International Airport (JFK) nonstop to San Juan, Puerto Rico (SJU) being operated with a Boeing 747 with the continuation of Pan Am flight 295 from San Juan nonstop to Port of Spain (POS) being operated with a Boeing 727 with through passengers from New York City to Port of Spain being required to change aircraft in San Juan. ^[3]

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.^[4] 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).^[1]