Originally Posted by
WineCountryUA
Generally if not a UA caused issue, you will be rescheduled for the next available UA flight. It will be your choice to accept economy if no business space. No downgrade compensation. You will be eligible for a partial fare refund.
This is more what is called a "flat tire" situation.
The other choice is for you to have UA move you to another carrier -- but you will be responsible for any fare difference.