An investigation of the principles of flight introduced Science Teacher Alex Randhava's Grade 7 students to the concept of air density. They assembled a wind tunnel and built aircraft with wing profiles that can generate lift. If the designs are fore-and-aft balanced, low-mass, and possess a wing profile that develops a zone of low pressure over the wing and concentrates air beneath it, they will fly. Students connected their models to a tether inside the wind tunnel, turned on the fan and watched as their craft fought against gravity. The exercise was inspired by work done by the Wright brothers during their research into wing profiles. In their larger wind tunnel, the wing was connected to a mass balance, and design improvements became measurable as the balance reflected a decrease in the effect of gravity on the wing.