Wait....there's a regular flight not yet mentioned, LAX to SNA which has got to be less than 50 miles, although I don't know what type of plane.

I've seen it a few times come up a few times when checking flights from SJC to SNA on aa.com (and if memory is right, the LAX to SNA leg is on United). I've never tried SJC-LAX-SNA, but seeing all the mileage related posts could inspire me to go for the extra miles if some day there's no time constraints for me to get to SNA.