With the United States now down to 4 network carriers, it's become harder.

American and United both offer nonstop service from LAX to Orlando, and fairly easy connecting service to DTW (AA over ORD, with DFW a little more out of the way; UA over DEN or ORD, with IAH being a little more out of the way).

American offers challengers for a fee; United will offer a challenge of flying X miles/segments in 90 days.

I've heard that LAX-MCO on United can be a tough upgrade, as Disney has a corporate contract on that route for those that need to travel between Mouse House East and Mouse House West/Corporate. Quality wise in F, I'd say Delta probably has the better experience (minus the meal service).