The TWA name when away as it was acquired by AA
TransMeridian Airlines
National Airlines (Las Vegas) disappeared
Midway Airlines
Vanguard Airlines out of MCI around 2002
Hooters Air disappeared (more or less, I think it's parent company Pace air still flies)
The short lived Legend Airlines out of Love Field in Texas
Caribean Sun
http://en.wikipedia.org/wiki/Caribbean_Sun
The original Pan Am completed it's final payment to former workers after a lawsuit was settled with Libya
Access Air
http://en.wikipedia.org/wiki/Access_Air
America West (bought out USair, but kept the USair name)
Independence Air
Chicago Express after ATA went Chaper 11
http://en.wikipedia.org/wiki/Chicago_Express_Airlines
Great Plains Airlines
http://en.wikipedia.org/wiki/Great_Plains_Airlines
I had never even heard of Pro Air until I found it here:
http://en.wikipedia.org/wiki/Pro_Air
Or Reeve Aleutian Airways up in Alaska:
http://en.wikipedia.org/wiki/Reeve_Aleutian_Airways