In a flight database that I'm working with on a project, there is a column of data called "flightCategory" with values "C", "G", "T", etc. Any idea what those actually mean? From what I understand, the database is from FAA. But I'm not 100% sure.
I got the answer. 'C' is commercial, 'G' general aviation, 'T' taxi, etc.
http://www.faa.gov/air_traffic/publications/atpubs/fss/AppendixA.htm, under section "Type of flight", it lists
S if scheduled air service
N if nonscheduled air transport operation
G if general aviation
M if military
X if other than any of the defined categories above.
But types C and T isn't there.