When Pigs Fly was released in July 2016 and is in fact a copy of another NetEnt slot game, Reel Rush.
The game comes with double stacked normal symbols on all reels and wild symbols on reels 2, 3, 4 and 5 only.
You start with 135 ways. And each time you get a winning combination during the same spin you will get a new re-spin and more ways open up. Until you have opened up the maximum of 3125 ways.
Once all 3125 ways are open (after 6 winning spins during the same bet) you start the free spins feature. You are awarded with 8 free spins and all free spins are played with 3125 ways. You can’t win more free spins during this feature.
It is a very unique way of playing. I don’t know any other slot games (except Reel Rush) that opens up more ways while playing.
When Pigs Fly uses a funny, cartoon-like, theme with pigs in space. And comes with a return to player percentage of 97%. Which is pretty good for an online slot game.