Trade secret: for the last 10 years, reviewing PC flight games has been a piece of cake. Step one - rabbit on about the fun-quotient, physics, visuals, missions and multiplayer for a bit. Step two - slip on the knuckledusters and deliver the kidney punch: "Of course, if you're after superlative sky thrills, you're still far better off with Crimson Skies." One of the reasons why the likes of Blazing Angels, Secret Weapons Over Normandy, HAWX and Heroes Over Europe have never managed to topple this cloud-couched charmer is that none of them have half its character. Set in an alternate 1930s where gangs of air pirates prey on the giant zeppelins that have superseded ships and trains, the game has a freshness and coherence to its fiction that makes most World War II or modern backdrops seem ditchwater-dull. Zipper Interactive can't take all the credit for the shimmering lore. Much of the inspiration came direct from Jordan Weisman and Michael Stackpole's 1998 board-game, which in turn enthusiastically plundered the treasure chamber that is American pulp radio, cinema and literature.