What are the differences between these three? Why do they send you three different identifying codes?
52.7k 18 18 gold badges 165 165 silver badges 275 275 bronze badges asked Oct 27, 2015 at 4:10 281 1 1 gold badge 3 3 silver badges 3 3 bronze badges Who are "they" in this question? Commented Oct 27, 2015 at 11:33The eTicket number (which is exactly the same as a paper ticket number) is your actual travel document's identifier. The ticket number is determined by the airline that tickets your trip (not the travel agent) and is used to track finances through the various airline reporting agencies. The first three digits identifies the airline that issued the ticket (which is not always the airline you are flying on).
The Itinerary Number, as Burhan mentioned, is simply a tracking number for the specific reservation system you booked through, be it an OTA (online travel agency), a bricks & mortar agency, tour company, etc. It is really only applicable when talking with the agency/agent that did your bookings. The GDS (global distribution systems - travel networking systems used by travel agencies) also issue their own Itinerary Number or Booking ID.
The Booking Reference, also know as a PNR (Passenger Name Record) or Record Locator, is the airline's internal identifier for your flight booking within their computer system. It is generated by the airline's computer system, not the travel agent or GDS. If your flights involve different airlines, there is often separate PNR's for each carrier for use within their respective systems, but you may be given only the ticketing airlines PNR (unless you ask specifically for all). When speaking directly with the airline you will be flying on, you will need to know the PNR for that specific airline.
As is always the case, there are always exceptions, as some airlines (such as major players in alliances) share more data with each other allowing them more flexibility with accessing reservations (such as referencing by another carrier's eTicket, etc)