The model sigma is an unusual paper airplane. It is relatively slow for a dart-type, but it has decent range and accuracy.
What you need to make this: 1 sheet of 8.5x11 printer paper, a stapler, and some type of hard object for creasing (my choice was an old battery)
Step 1: Fold Paper in Half Lengthwise
Step 2: Fold Corners Down
Be sure that the edge is lined up with the primary fold.
Step 3: Repeat Step 2
Step 4: Repeat Step 3 (twice)
Now you should crease the folds using the "hard object" because of how thick the paper is getting.
Step 5: Fold Up Wings
Take the two outer layers of paper and fold them out.
Step 6: Staple Fuselage
Put three staples evenly spaced out along the fuselage.
Step 7: Pull Out Wings
With the plane turned upside down, grab the top layer (from your perspective) of the wing and pull it out. Your plane should now resemble the second picture.
Step 8: Finished
If your plane does not resemble the picture, you did something wrong.