This is how you control your character while flying/gliding. The following instructions are geared toward Two-Handed Mode but functions are similar in One-Handed Mode, the only major difference in where the d-pad is located on the screen.
When in the air you will normally be placed into closed wing mode. Slide your finger on the d-pad area to navigate in the air. You can think of this like a "hover" or "helicopter" mode.
While in the air tap the open wing button, which appears above the jump button, to enable the ability to dive and climb. You can climb more in windy areas. You can think of this like a "glider" or "airplane" mode. Tap it again to go back into closed wing mode.