Some aircraft, such as the I-15, SB and Su-2, have a little tab in the top left corner of their icon these are stacks of planes, if you click one then a window should pop up with two or more variants of that plane. To unlock a specific plane you’ll need to have researched the previous plane in its line (connected via an arrow). To progress through the ranks you need to unlock a certain number of aircraft, shown under the Roman numeral on the left in the screenshot I’ve got three Rank I aircraft and need six in total before I can research a Rank II aircraft, then I’ll need to research four of Rank II before I can start on Rank III.

Premium aircraft are bought with Gold Eagles (the real money currency), and don’t need to be researched Gift aircraft are generally available in bundles, or sometimes in promotions or giveaways. Over on the right hand side of the tree are Premium and Gift aircraft, with a yellow/gold background. Aircraft you own have a blue background, aircraft you can research have a slightly darker blue background, aircraft that aren’t available for research yet have a red background. The Russian tech tree not to be confused with the Russian techno treeĪircraft are divided into five ranks or eras, broadly chronologically but with some adjustments to account for performance in a game context, for example the German Do 217 J series heavy fighters in Rank II are derived from the Do 217 E bomber in Rank III.

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