It was not originally just a mileage run, but it turned in to one since I did not have enough time to leave the airport and attend my meeting and come back the same day. I said I was satisfied with what I got, (I can use a UA voucher just as much as a refund), but I was curious how UA and others apply Trip In Vain. E.g. do you have to be delayed a predetermined number of hours to quallify for TIV? Is TIV some kind of published rule or an urban legend? How do TIV procedures differ airline to airline?