By design
A first division by design among aircraft is between lighter-than-air and heavier-than-air aircraft.
Examples of lighter-than-air aircraft include non-steerable balloons, such as hot air balloons and gas balloons, and airships (sometimes called dirigible balloons), such as blimps (which have a non-rigid construction) and rigid airships, which have a rigid frame.
The best-known type of rigid airship is the Zeppelin.
In heavier-than-air aircraft, we can discern two major ways to produce the lift: aerodynamic lift and engine lift.
In the case of aerodynamic lift, the aircraft is kept in the air because of aerodynamics, usually by means of wings of some kind.
With engine lift, the aircraft defeats gravity by sheer engine power.
Examples of engine lift aircraft are rockets, and so-called VTOL planes, such as the Hawker Harrier.
Among aerodynamically lifted aircraft, the largest number falls in the category of fixed-wing aircraft, where horizontal surfaces produce lift, by profiting from the Coanda effect (aeroplane or airplane).
In a "conventional" configuration, the lift surfaces are placed in front of a control surface or tailplane. The number of lift surfaces varied greatly in the pre-1950 period, as biplanes (two wings) and triplanes (three wings) were numerous in the early days of aviation. Subsequently most planes are monoplanes.
The reverse configuration is the canard type, where small horizontal control surfaces are placed forward of the wings, near the nose of the aircraft.
Other possibilities include the delta-wing, where lift and horizontal control surfaces are combined, and the flying wing, where there is no separate vertical control surface (e.g. the B-2).
A variable geometry ('swing-wing') has also been employed in a few examples of combat aircraft (the F-111, Panavia Tornado, and B-1 Lancer, among others).
The lifting body configuration where the body itself produce lift has been tested. So far the only significant practical application of the lifting body was in the Space Shuttle.
A second large category of aerodynamically lifted aircraft are the rotary-wing aircraft. Here, the lift is provided by rotating rotors. The best-known examples of this category are the helicopter, the earlier autogyro, and the tiltrotor aircraft (such as the V-22 Osprey).
A further category might encompass the wing-in-ground-effect types, for example the Russian ekranoplan, also nicknamed the "Caspian Sea Monster" and hovercraft, most of the latter employing a skirt and achieving limited ground or water clearance to reduce friction and achieve speeds above those achieved by boats of similar weight.
And finally, the flapping-wing ornithopter is a category of its own. These designs may have considerable potential but are not yet practical.
