Utica and Syracuse Air Line Railway in New York (never built)

Webster's 1913 dictionary gives the definition "Air line, a straight line; a bee line. Hence Air-line, adj.; as, air-line road." (As of 2005 this meaning has fallen into disuse.) Air line railroads began to be built in the mid-nineteenth century; in 1853 the New York Daily Times ran a satirical article mocking the trend, and the exaggerated investment prospects associated with them:

Milltown Air Line Railway, a logging railroad in Georgia

New York and Pittsburgh Air Line Railroad, part of the Pennsylvania Railroad

Montreal and Boston Air Line, a marketing name used by the Boston and Lowell Railroad

New York and Boston Air Line Railroad, part of the New York, New Haven and Hartford Railroad

Fargo and St. Louis Air Line Railway, part of the Chicago, Milwaukee, St. Paul and Pacific Railroad

St. Clair and Chicago Air Line Railroad, part of the Grand Trunk Railway

Northern Nebraska Air-Line Railroad, part of the Chicago and North Western Railway

St. Louis, Oklahoma and Texas Air-Line Railroad, part of the Chicago, Rock Island and Pacific Railroad

Chicago and Indianapolis Air-Line Railroad, part of the Chicago, Indianapolis and Louisville Railroad

Piedmont Air-Line Railway, part of the Southern Railway

Le Roy and Caney Valley Air Line Railway, part of the Missouri Pacific Railroad

Kansas City and Independence Air Line Railroad, part of the Kansas City Southern Railway

Seaboard Air Line Belt Railroad, part of the Seaboard Air Line Railroad

Stillmore Air Line Railway, part of the Central of Georgia Railway

Seaboard Air Line Railroad/Seaboard Air Line Railway, a major system in the U.S. South, now part of CSX

Air-Line Railroad of North Carolina, part of the Southern Railway

Air-Line Railroad of South Carolina, part of the Southern Railway

Atlanta and Birmingham Air Line Railway, part of the Seaboard Air Line Railroad

Atlanta and Charlotte Air-Line Railway, part of the Southern Railway

Atlanta and Richmond Air-Line Railway, part of the Southern Railway

Chicago and Indiana Air Line Railway, part of the South Shore Line

Chicago-New York Electric Air Line Railroad, a short interurban streetcar line near Chicago, Illinois

Cincinnati and Chicago Air-Line Railroad, part of the Pennsylvania Railroad

Eufaula and St. Andrews Bay Air-line Railroad in Florida (never built)

Santa Monica Air Line in Los Angeles County

St. Charles Air Line Railroad in Chicago, Illinois

Virginia Air Line Railway, part of the Baltimore and Ohio Railroad

Waycross Air Line Railroad, part of the Atlantic Coast Line Railroad