Greatest one ever, which pre-dated FT was the Pan Am shuttle "Book" promo which they ran several times in 1989/1990/1991. One could buy a book of 10 Pan Am shuttle tickets for something ridiculous like $399. As the shuttle operated on a "show up and fly" service, there were no blackouts or other restrictions. Each shuttle segment also earned 1500 miles, and they had a couple of other promotions including, a thousand bonus miles per same day roundtrip, as well as a 20,000 bonus if you flew 10 segments in a month, lastly there was at one point a $!00 discount on the book if you were a student.

So for $299, if one spent the entire weekend just flying back and forth, one would earn 15,000 miles "regular", 5,000 miles for same day RT's, and 20,000 for flying 10 segments on a month, a total of 40,000 miles. I should also note that IIRC one would earn Platinum status at 30,000 flown miles, so if one did this twice, one would have Platinum status. And in those days unless you were flying to Europe Platinums always got upgrades, Economy RT's to Europe cost 30,000 miles and business 40,000 miles (it might have been 50). So if you did this twice you got two RT flights to anywhere they flew in Europe and even had a good shot to get upgraded to First. Rack rate on these even at that time was $5k for J and $8k for F, and it cost a whopping $600 bucks. I remember once doing this and seeing an Indian family of 8 doing the same thing all weekend to get their tickets to India.

Another one of that era were the "Standby passes" that US carriers would sell to foreign students. They generally cost $599 and for a month gave non-US people under the age of 23 (could have been 25 IIRC) the right to fly UNLIMITED standby anywhere the airline flew in the US, All the big carriers had a version of these, Delta, American, United, TWA, Pan Am, etc. There were two things however that the airlines did not think about. One, it was an era of much less security when it came with documents, and the tickets were essentially written on the spot at the gate, so clever foreign students figured that if there were two of them, one would get the ticket written up, pass the book over to their friend before boarding (if there was space on the plane, the seat could be confirmed and BP issued 2-3 hours before the flight) and then their companion would just fly in on the next flight. Yes a bit of fraud, but I do know non US citizens who did this.

The FF aspect of this, that I suppose the airlines were myopic about was that some clever students would open a FF account with the airline, save all their boarding passes from these flights and then send them all in after the month was over and get full FF credit for all the flights that they made. So I remember a British friend of mine bragging about how he had flown, all across the US back and forth 7 times including Hawaii etc with his friend for $599 and then flew back the next year from Europe to the US again RT the next year with the miles that he earned from it. Obviously the world is a much different place now, but things like this did happen in the 80's and up to the early 90's.