I was attempting to use the BTS on time statistics database online to look up tail numbers.
The tail numbers it provided didn’t make sense, and did not correspond to the actual aircraft.
Is there a method to deciphering them, or am I looking in the wrong place? They have been correct in the past, but using the online lookup tool, it didn’t seem to work.
Any help would be appreciated.
The tail number used in the BTS is actually the fleet number - the number the airline uses internally. Different airlines used different systems.
Southwest uses the three digits in its aircraft “N” number. examples: N453WN is N453 and N999LV is N999. Because Southwest does use the registration as the fleet number, you’ll never find any 2 aircraft with the same digits in the “N” number.
American and Continental, among others, have their own internal system. If I recall correctly, Continental assigns its numbers based on aircraft type.
The book *JP Airline Fleets International *shows the fleet numbers. I haven’t found a list of fleet numbers on the Internet. If you have the time, you may wish to try the search your self. Remember that another term for fleet number is ship number.
If you want to have a few numbers decoded, you can send me a private message. Just try to keep it to 5 or so for no more than 2 or 3 airlines! 
I took a look at the data in the BTS database. I downloaded the data for January 2009. With the exception of Pinnacle (9E) and American (AA), all of the airlines seem to be reporting the actual “N” number.
Pinnacle’s aircraft are either the CRJ200 or CRJ900. I’ll have to look in the JP Airlines Fleets book to see how American’s numbers tie up to the N numbers.
Thanks for your response.
The ones I were attempting to decode were FLG flights! 
Other ones I figured out.
I will look in to JP Airline Fleets International…
I’ll try and explain the Flagships (the CRJ2’s anyway), they usually show as “80279E” or “84329E” for example. If you ignore the last two digits of “9E”, you are left with “8027” and “8432”. These correspond to the registration number minus the last letter. Note that the ones listed from 8000 to 8041 are actually the construction (serial) number of the aircraft, and the registrations are from N800AY to N841AY. The other one, “8432” is N8432A so if you just make a note of the first four numbers and look in the JP, you should find the registration.
Hope you could understand all that
Makes sense. Thanks for the suggestion!