What is the main source of lift in a commercial airliner?

Lift is the force that holds an aircraft in the air. It can be generated by any part of the airplane, but most of the lift on a normal airliner is generated by the wings. An aerodynamic force, lift is produced by the motion of a fluid past an object, as it acts through the center of pressure of the object, perpendicular to the flow direction. Being a mechanical force, lift can only be generated by the interaction and contact of a solid body with a fluid (liquid or gas). It is not generated by a force field, in the sense of a gravitational field, or an electromagnetic field, where one object can affect another object without being in physical contact. For lift to be generated, the solid body must be in contact with the fluid: when there is no fluid, there is no lift. For example, the space shuttle does not stay in space because of lift from its wings but because of orbital mechanics related to its speed. Space is (nearly) a vacuum. Without air, there is no lift generated by the wings.

Source: NASA