Instructions
Lay out the base of the fuselage. The fuselage is the main part of the plane, the body. The base is the lower-most LEGO layer, to which you will later attach the walls, nose, tail and wings of the plane. Make the base out of flat plates, several of them in a row. You should use at least 4-stud wide plates, but probably not much more than 6-stud wide plates.
Add any seats, chairs or other internal parts that will be in your plane. Most planes have several rows of seats for passengers, or lots of equipment inside.
Build the walls of the fuselage. Add a row of 1-stud wide bricks around the edge of the base, and overlap the gaps on the lower rows to create a solid piece.
Build a nose and tail on the plane. At the front and rear of the fuselage, add plates that taper to a nosecone and tail-cone. Surround these new sections with more bricks.
Add another layer to the fuselage, nose and tail, making sure to place bricks over the gaps on the lower row to create a stronger piece of the plane. Build at least five layers, to create tall walls that will surround a LEGO figure.
Build the cockpit in the nose section. This is where the pilot sits, and where all of his instruments are laid out.
Build a tail fin and spoilers. These parts are at the rear of the plane, attached to the tail section. Two small wing-shaped flaps, which lie horizontally, and an upright fin in the center. Some airplanes have different configurations, although most will look like an upside-down T from behind.
Turn the fuselage over and add landing gear. Most planes have several wheels on the bottom which are used when landing--although some aircraft replace those wheels with pontoons and land on water instead. These wheels should steady the plane when it's turned over.
Build the wings. You need two symmetrical pieces that are long and wide--the wingspan needs to be at least the same length of the plane, and the wings should be wider than the tail flaps are. Many large airplanes also have the engine on the wings, although some designs have nose-mounted propellers.
Attach the wings to the airplane. Depending on the size of the aircraft, the wings will be either attached to the top or the bottom. Smaller airplanes have higher wings than larger aircraft.
Build the roof of the airplane. Try to use rounded or angled parts, to give a streamlined look. Most airplane sets made by LEGO include a hinged roof, which allows you to lift the top of the plane sideways and look inside.