Instructions
Go to Shoreside Vale airport. Three Dodo Planes will appear as dots on your map. Each plane is the same so it makes no difference which one you take.
Go to one of the Dodo Planes located on your map and enter the cockpit by pressing the "A" button. Use the directional pad to drive the Dodo Plane to the end of the runway and line it up straight. Left and right will turn your plane to the appropriate direction; use Up to accelerate and Down to deceleration.
Press Up on the controller and speed down the runway. Do not veer off the runway as driving across the grass will cause you to lose speed. You will begin to accelerate and point the nose of the plane downwards. Eventually you will see sparks indicating that the plane is reaching maximum speed.
Let go of the Up button. The Dodo Plane will begin to rise quickly from the runway, so keep tapping the Up button to keep the rise steady and prevent it from flipping around.
Keep the plane leveled. Change camera angles using the back shoulder buttons on your controller to help you maintain balance. After a few moments, the Dodo will stop rising, but do not do anything--leave the controls alone. The Dodo Plane will regain its flight momentum and keep going.
Tap the Left and Right buttons to bank the Dodo. The plane is quite capable of making sharp turns but never press the Down button as this will force the plane to stop and lose speed.