Originally Posted by
sbm12
What you are describing is throw-away ticketing and is a violation of the contract of carriage. Doing it once or twice won't get you in a lot of trouble. Doing it a lot will.
I'd add to smb12's response that you could very well have a problem if you do this on the OUTBOUND rather than the RETURN. If you book SJO-IAH-LAS-IAH-SJO but try to fly SJO-IAH/IAH-SJO, you can get off at IAH on the outbound but your return will probably be cancelled because you didn't show up for IAH-LAS