|Major air carriers||N||N||N||N||N||13||14||11||12||13||13||13||15||15||15||14||14||17||21|
|Other air carriers||N||N||N||N||N||89||56||85||84||83||83||81||76||72||68||66||69||65||77|
|Class I railroads||106||76||71||73||39||25||14||11||10||9||9||9||8||8||7||7||7||7||7|
|Interstate motor carriersb||U||U||U||U||U||U||216,000||346,000||379,000||417,000||477,486||517,297||560,393||592,909||600,104||674,314||677,317||679,744||U|
|Marine vessel operatorsc||U||U||U||U||U||U||U||1,381||1,348||1,311||1,235||1,174||1,114||1,063||877||798||767||733||682|
|Pipeline operatorsd||N||N||1,123||1,682||2,243||(R) 2,163||(R) 2,198||(R) 2,367||(R) 2,327||(R) 2,281||(R) 2,236||(R) 2,238||(R) 2,157||(R) 2,135||(R) 2,186||(R) 2,216||2,240||2,166||2,297|
|Hazardous liquid||N||N||N||N||N||(R) 171||(R) 171||(R) 197||(R) 205||(R) 216||(R) 219||(R) 215||(R) 220||(R) 220||(R) 218||(R) 235||(R) 278||(R) 302||324|
|Natural gas transmission||N||N||420||432||474||724||866||975||971||957||889||885||844||(R) 837||(R) 919||(R) 947||(R) 941||(R) 968||992|
|Natural gas distributione||N||N||938||1,500||1,932||1,485||1,382||1,444||1,397||1,365||1,375||1,393||1,363||1,341||1,331||(R) 1,311||(R) 1,344||(R) 1,352||1,325|
KEY: N = data do not exist; R = revised; U = data are not available.
a Carrier groups are categorized based on their annual operating revenues as major, national, large regional, and medium regional. The thresholds were last adjusted July 1, 1999, and the threshold for major air carriers is currently $1 billion. The other air carrier category contains all national, large regional, and medium regional air carriers. Beginning in 2003, regional air carriers are not required to report financial data which may result in under reporting of "Other carriers" in this table.
b Figures are for the fiscal year, October through September. The Federal Motor Carrier Safety Administration deletes motor carriers from the Motor Carrier Management Information System (MCMIS) when they receive an official notice of a change in status. This most often occurs when a safety audit or compliance review is attempted. As a result, inactive carriers may be included in the MCMIS.
c The printed source materials do not contain totals for the number of operators and data files from which the figures can be determined are not available prior to 1993.
d There is some overlap among the operators for the pipeline modes. Therefore the total number of pipeline operators is lower than the sum for the three pipeline modes.
e In 1975 and 1980, natural gas distribution includes master meter and mobile home park natural gas distribution operators. A master meter system is a pipeline system for distributing gas within, but not limited to, a definable area, such as a mobile home park, housing project, or apartment complex, where the operator purchases metered gas from an outside source for resale through a gas distribution pipeline system. The gas distribution pipeline system supplies the ultimate consumer who either purchases the gas directly through a meter or by other means, such as by rents.
1960-2002: U.S. Department of Transportation, Bureau of Transportation Statistics, Office of Airline Information, Air Carrier Financial Statistics Quarterly (Washington, DC: Fourth quarter issues), "Alphabetical List of Air Carriers by Carrier Group ...".
2003: Ibid., personal communication, Oct. 5, 2004.2004-06: U.S. Department of Transportation, Bureau of Transportation Statistics, Office of Airline Information, Air Carrier Financial Statistics Quarterly (Washington, DC: Fourth quarter issues), "Alphabetical List of Air Carriers by Carrier Group ".
1960-85: Association of American Railroads, Railroad Ten-Year Trends, Vol. 2 (Washington, DC), table I-2.1990-98: Ibid., Vol. 16 (Washington, DC: 1999), p. 10.
1999-2006: Ibid., Railroad Facts (Washington, DC: Annual issues), p. 3.
Interstate motor carriers:
1990-2001: U.S. Department of Transportation, Federal Motor Carrier Safety Administration, Motor Carrier Management Information System, and personal communication, Nov. 6, 2001.
2002-05: U.S. Department of Transportation, Federal Motor Carrier Safety Administration, Analysis and Information Online, available at http://ai.volpe.dot.gov/mcspa.asp as of June 4, 2004, and personal communication, January 2007.
Marine vessel operators:
U.S. Army Corps of Engineers, Waterborne Transportation Lines of the United States, Volume 1, National Summaries (New Orleans, LA: Annual issues), table 13.
U.S. Department of Transportation, Office of Pipeline Safety, Gas Distribution Systems, Gas Transmission & Gathering Systems and Hazardous Liquid Pipeline Systems Annual Reporting, and personal communication, as of September 2008.