What are the 2, 3, and 4 digit sic codes for this passenger airline
industry?  What are the five largest parent companies in the airline
passenger industry listed with their total sales?

According to the Air Transport Association, the five largest U.S.
airline passenger carriers are:

1.	American Airlines (AMR) $19 billion in FY 2001
2.	United Airlines (UAL) $16.1 billion
3.	Delta (DAL) $13.9 billion
4.	Northwest (NWAC) $9.9 billion
5.	Continental (CAL) $9 billion

Revenues are from Hoover's Information Service:
www.hoovers.com

The four-digit SIC code is also on the Hoover's site: 4512.  SIC codes
can be truncated from the 4-digit to 3- and 2-digit codes.  The 1987
SIC codes have been converted by the U.S. government to the new NAICS
codes, adding about 350 types of new commercial businesses.  A
detailed list of SIC codes and their newer forms are here in "SIC to
1998 NAICS":
http://www.naics.com/files/sic2naic.htm

Google search strategy:
Use Hoover's for revenue numbers
"SIC code" + NAICS for precise classifications

Best regards,

Omnivorous-GA