Complex sentence: City and state representatives from California and New York led the support for the airline, while the biggest opposition came from a national aviation labor union, Air Line Pilots Association, as well as the pre-existing Houston, Texas-based competitor Continental Airlines.
Split into simpler sentences: City and state representatives from California and New York led the support for the airline. The biggest opposition came from the Air Line Pilots Association (a national aviation labor union) and existing competitor U.S. airlines led by Houston-based Continental Airlines.