I've been here since 1999, under various usernames, so...
TWA
Canada 3000
Ansett
I *almost* saw the merger of Aloha and Hawaiian glad that didn't happen.
Sabena
Swissair
Caledonian
Canadi>n
Midway
II
National
II
Vanguard
AccessAir
Royal Tongan
Condor (Became Thomas Cook)
JetsGo
VASP
Transbrasil
Khalifa Airways
Ghana Airways
Nigeria Airways
Air Bourbon
JAS
Impulse Airlines
Kendell
Air Aruba
Laker Airways
Aeromar
Air Guadeloupe
Air Martinique
Dutch Caribbean Airlines
Air Caribbean
Lauda Air
Citybird
VG Airlines
Air Littoral
AOM
Aero Lloyd
Olympic Aviation
Air Holland
DutchBird
Debonair
Go Fly
JMC
Tango
Royal Aviation
Zip
Airborne Express
ACA (became Iair)
Emery Worldwide
Reeve Aleutian
Reno Air
United Shittle
Tower Air
LAPA
Rio-Sul
Transbrasil
ACES Colombia
AeroPeru
Faucett
and now, America West.
That's not even all of them according to that wiki article. But dang, so many.
