I recently scheduled a flight through cheapair.com as usual and the ticket came back issued by only American Airlines that included a return Frontier flight as well. The result is not being able to change the return leg of my trip without huge penalties.
I am a loyal frontier customer with Summit status which means I can change flights without penalties at any time. After speaking with a cheapair representative to try and change my return flight leg, I learned that their auto-ticketing system which is "out of their control" is to blame for the tickets being combined and uneditable. This is highly disappointing as nowhere on their website or my confirmation email does it state that this was a combined ticket, resulting in not being able to change it without huge penalties.
I will no longer use cheapair.com as I have in the past due to this issue. I will use the airline websites to book instead, as I know the tickets will be separate and able to be modified.