I just had an issue on UA where I missed a connecting flight.

I am about to try for a DFW - PPT award ticket on via SA with DFW-LAX on UA and LAX-PPT on ANZ.

What happens if UA is delayed and I miss the ANZ flight?? It's not like they have a lot of these flights....

I would imagine I will hear "make sure you have a few hours extra at LAX" which I will of course do, but what normally happens? I am interested due to my hopefully upcoming trip and actually just curious outside of that...