It’s because you’re not increasing the variable while the input action for forward movement is pressed, or decreasing while the input action for backward movement is pressed. You should only plug in the variable as it is into the Set Max Fly Speed node after the Event Tick to update it continuously. The adjustment of the value should be handled after those input actions separately. To increase / decrease you can use ++ / - - nodes respectively, as simply using the addition node wouldn’t actually adjust the variable itself. And also make sure to add a delay before the increase / decreases