Planes "tilt" (or "rotate") when taking off primarily to increase lift by changing the wing's angle relative to the oncoming air. According to the physics of aerodynamics, as a plane speeds down the runway, the pilot pulls back on the controls to move the "elevators" on the tail. This pushes the tail down and the nose up, increasing the Angle of Attack. This steeper angle forces air to move faster over the curved top of the wing and pushes more air downward, creating the upward force needed to lift the massive weight of the aircraft off the ground. Additionally, this tilt helps clear the landing gear from the runway surface and positions the plane for its initial "climb phase." The specific angle is carefully calculated based on the plane's weight and the air density to ensure the aircraft reaches its "rotation speed" (Vr) safely without stalling or dragging the tail on the tarmac.