From Phil:
I found a possible explanation why there is no history of N644AA in the
BTS data base.  It's because AA sometimes reports the tail number
using a fleet number, not the registry number.   The fleet number for
N644AA is 5BP, so the number reported to BTS was N5BPAA, not N644AA.
Once you use the reporting number N5BPAA, then N644AA DOES have a
flight history in the BTS data base.
This explains another mystery, why you get an error message ("The
registry number cannot contain more than two alpha characters") when
you try to look up 5BPAA as a registry number on the FAA N-Number
Inquiry screen, while there are many "registry numbers" with four
alpa characters in the BTS data base.
"19. Odd N Numbers and info on the BTS
I think I can clear up some of your confusion about the odd looking
tail numbers in the Bureau of Transportation's On Time reports . . .
For some reason AA frequently reports the tail # using their internal
fleet number, but there is a way to convert them. The fleet number is
the number and two letters between the "N" and the "AA". Based on
what I can tell, if the number after the "N" is a "5" then it's a
757, if the number is a "3" it's a 737 and if it's a "4" it's a MD-80
or variant.
Even though the final update was December, 2002 you can still find a
lot of these at Bill Harm's old Commercial Jet Aircraft Census
website.  [Found at]
For instance if I want to know what plane N5BPAA is and I know that
the plane is a Boeing 757, go to the 757 page at:
and then if you have a "find" button on your keyboard, look for the
middle three numbers (between the "n" and the "aa" ex: find "5BP" and
it should scroll right down to the aircraft. N5BPAA is N644AA, the
aircraft that operated as Flight 77."



Potential issue: Flt 77 Tail number (Registry number) missing
There appears to be a bit of a problem with the airline on-time data 
reported to the Bureau of Transportation Statistics (BTS).  The 
history of flights made before 9/11 by the plane with registry number 
N644AA, which, as flight AA77, allegedly crashed into the Pentagon, 
is missing.  This was first noticed by Aidan Monaghan, who posted his 
observation on The implications 
are puzzling.
According to the web site of the BTS, "Airline on-time data are 
reported each month to the U.S. Department of Transportation (DOT), 
Bureau of Transportation Statistics (BTS) by the 18 U.S. air carriers 
that have at least 1 percent of total domestic scheduled-service 
passenger revenues, plus two other carriers that report voluntarily. 
The data cover nonstop scheduled-service flights between points 
within the United States (including territories) as described in 14 
CFR Part 234 of DOT's regulations. Data are available since January 
For each flight, the reported detail data includes the originating 
airport, the destination airport, airline code, date of flight, 
flight number, registry number (aka tail number), scheduled and 
actual times, et al.  All this data is stored in a data base that may 
be accessed by the public via the above mentioned BTS web page.  
Monthly reporting of this data is mandated by law.  See Code of 
Federal Regulations, Title 14, Volume 4, Revised as of January 1, 
2002, 14CFR234.4.
Although the detail data elements pertain to particular flights, it 
is possible to manually link flights together by registry number so 
as to plot a history of the flights made by a particular plane.  I 
have done this for 9/11 planes N334AA (AA 11), N591UA (UA 93), and 
N612UA (UA 175), going back 5 days previous to 9/11 (see attachment). 
The quality of the data in the data base is far from perfect.  Some 
data is missing, such as the September 8 and 9 flights of the plane 
with registry number N612UA.  (How did the plane get from Boston on 
September 7 to JFK on September 10?)  For N591UA on 9/9 there is an 
arrival (at ORD) record but no departure (from SNA) record for the 
same flight.  In some instances the flight number is duplicated (UA 
627 on 9/6; UA 528 on (9/9).  The registry number may be missing, in 
which cases the value "UNKNOW" is used.
It is particularly noteworthy that there is no BTS flight data at all 
for a plane with registry number N644AA (flight AA 77 on September 
11) in the data base.  The BTS data for flight AA 77 on 9/11 shows 
that a plane with an "UNKNOW[N]" registry number, not N644AA, was 
scheduled to depart from Dulles International for Los Angeles