It's a Classic!
Just got out a piece of A4 in order to remember how it is done. Strange to say a mate at Primary School showed me this one back in Mumble 60 something.
Errr..
1) Fold in half length ways.
2) Fold 'front' to make a right angled triangle.
3) Open up and fold over front to vertex of triangle.
4) Fold back in half and tear off square bit form open edge of triangle.
5) Open up and re-fold other corners of previous triangle to centre to create pointy bit.
6) Re-fold previous triangle so torn corners are foremost.
7) Fold torn corners to centre in a triangular manner.
8) Fold pointy bit between torn corners now at centre.
9) Reverse fold length ways so pointy bit holds rest in place.
9) Fold Wings.
10) Extend wings.
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http://i.imgur.com/RsrkmLz.jpg
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11) Go Fly
Erm E&OE