How can one determine the registration number (i.e. N123AA) of the aircraft used on a particular flight, having the date, airline, flight number and city pair to start with?
The step-to-step guide:
1. Search for Flight Number:
- Get hold of the flight number, such as LH123 or AA789 for instance. This is usually found on your ticket, baggage tag or some email.
- Enter it on a site such as www.flightradar24.com or www.planefinder.net.
- Note down the registration (such as N1234A or D-ABYT) for the flight on the day your are interested in.
2. Search for this Registration:
Try entering it on for instance www.planespotters.net which is often considered a reliable source for aircraft data.
You should be able to get the aircraft history:
- First flight and delivery dates (and hence aircraft age)
- Previous operators and registrations.
- MSN (manufacturer serial number)
The reg number's only set in stone once the plane takes off, so you'll only get this information for past flights. Equipment can and often does change between hops on the same flight number, and a multi-stop flight can even arrive at one gate and depart at a different one because of a scheduled plane change (or a last-minute one). The routing/scheduling center for the airline will know the expected equipment to be used, but that information doesn't technically become public until the flight plan for the hop is filed with the FAA, which for major airlines with pilots and ground staff coordinating each flight, can happen as late as the aircraft taxiing to the runway.
You can try http://www.flightradar24.com/. It's an aviation database of commercial flights updated in real time. Here are the most recent stats for Southwest flight WN3223, a trans-con multi-hop route from NY-Laguardia through Dallas Love, Phoenix, LAX, Oakland and Sea-Tac. There have been a few different tails used for this flight number over the past few days, including N7732A, N746SW and N260WN. This is common for Southwest, as they operate the B737 exclusively, and with very few exceptions any plane in the fleet can handle any route if need be (they did get some new -800s recently which have slightly higher passenger count so they're not completely interchangeable).
As you can see, information on tail numbers is not complete; it should be sufficient to assume the tail doesn't change between stops on the route unless a new one is specified. If you really have to know, the airline can probably tell you what equipment was used on a particular flight if you ask really nicely (or you have some input on possible maintenance issues), but they won't be able to guarantee a particular tail number for an upcoming flight unless the route is such that only one plane in their fleet could do it (which is rare and becoming rarer but still not unheard of).