Originally Posted by
jlemon
6. Continental, Hughes Airwest and Pacific Southwest Airlines (PSA) are all correct, of course.
Continental did indeed operate the B720B into Burbank followed by the B727-200. I remember flying on CO operated 72S equipment nonstop to DEN and SJC.
Hughes Airwest also operated DC9-30 flights nonstop from BUR to SLC with continuing service to DEN. I flew on this routing as well on board an RW D9S.
PSA operated a number of jet types into BUR over the years including the BAe 146, B727-100, B727-200, B737-200, DC9-30 and MD-80. And before the 727 showed up, the airline operated the Electra into the airport. Being born and raised in nearby Pasadena, I flew on PSA many times into and out of Burbank.
So that leaves us with only fourteen (14) more airlines to go! 
BTW, there is nonstop service these days between BUR and SAN.....operated by SeaPort with nine (9) pax, single turboprop engine Cessna Caravan aircraft. What indeed happened to that traffic from days of yore?!
OK, here are some more:
1. Republic
2. Western
3. AirCal
4. SunWorld - this "deregulation knockout" served BUR in 1986-87
5. America West
6. USAirways - successor to America West, now no longer with us.
7. Delta
I'm also going to throw out three wild guesses: Golden West, in the late 1960s, with one of their short lived Hansa Jets, WestAir in the late 1980s with BAe 146s, and Freedom Air in the early 2000s with Canadair RJ 700 / 900.