What airlines can you fly LAX-DEN???

American
Frontier (Denver is their major hub and LAX is a focus city)
United (Both Denver and LAX are major hubs)

United has 2000+ seats a day between LAX and DEN
6 Boeing 757's
3 Boeing 737/A320 sized aircraft
1 widebody Boeing 767
1 widebody Boeing 777

Even if ONLY United flew that route, you would be fine.

On top of that:
Frontier flies 6 A319's daily on that route.
American flies 4 MD-80's daily on that route.

Of all the commutes possible to be flown by airline pilots, LAX-DEN has to be on of the easiest.