Aircraft fly level when the red circle stay center of the circle. You can adjust level flight angle in OPTION screen.

Place Missile Seeker on target until Missile Lock-on turns red.

Eliminate all Target enemies on the radar.

Tilt aircraft left or right and tilt up. The aircraft make tighter turns.

How to level out in EASY mode. (View Point: Behind View, Control: Novice)
Press AUTO button to level out aircraft from any angle.