Columbia subject headings:
Airlines--United States.
Competition--United States.
Consolidation and merger of corporations--United States.
US Airways.
United Airlines.
Harvard subject headings:
Airlines--United States
Competition--United States
Consolidation and merger of corporations--United States.
US Airways.
United Airlines.
Princeton subject headings:
Airlines--United States.
Competition--United States.
Consolidation and merger of corporations--United States.
US Airways.
United Airlines.