Analog From United States of America, joined Jul 2006, 1900 posts, RR: 1
Reply 4, posted (8 years 5 months 1 week 2 hours ago) and read 4011 times:
For a ballpark estimate I would start by looking at the ratio of first/business seats to coach seats on aircraft used for domestic flights (don't forget regionals, which typically have a ratio of zero). Then multiply by the number of each aircraft in service, flights per day...
This assumes equal load factors for first & coach.