Skills start at Level 0 and and are locked until the Skill positioned above it in the tree, has been levelled up past Level 1.
Each Skill can be improved up to Level 3. Each Level costs 5 Skill Points and increasing the Level can improve the power or duration or the Skill or can decrease the cooldown time. Cooldown time is a measure of the time needed before the Skill is able to be used again.
Once Skill Points are allocated to a Skill they cannot be removed except by purchasing an item from the Premium Shop. There are four items in the Premium Shop, one for each Skill Tree. The Items are called Reset Common Skills (General), Reset Fighter Skills, Reset Gunner Skills (Recon) and Reset Bomber Skills.
Skill Points can be added to a Skill, in either the Hanger or the Item Shop tabs, by right mouse clicking on the Skill Icon and increasing the number of Skill Points allocated to this Skill. Be aware that once Skill Points are added to a Skill they cannot be removed.
For organisation, Skills are presented in a tree format and there are four trees: General, Fighter, Recon, Bomber.