You must have a reciprocating agreement with the company. Unlimited, but no F/A seat available. Frontier has always been one of the great airlines to JS with. Freindly no-hassle staff, TV, spacious seating and good food on the longer flights.
Please remember to introduce yourself to the crew. I'm amazed that, in spite of all these ammenities, there are a lot of 'professional pilots' who just hop in a seat as soon as they get on. This has been putting a lot of scrutiny on companies which have long reciprocated.