This is a perfect small project for Design and Technology in KS1 and KS2. It introduces the topic of Structures. The project will give the children the opportunity to follow instructions to make and test a paper aeroplane and some simple beams to show how the properties of paper can change with some simple folds. Use whatever you have as the weight.
If the children are really keen and enjoy the project, you could always extend it to make bridges and towers from either art straws, spaghetti or rolled up or folded paper.