Simon Bahr, an aerospace engineer, explains lift, the force that keeps a plane in the air, and describes the safety testing that planes go through before they are allowed to fly, in this video from WGBH and The Documentary Group. Bahr relates lift to the sensation you feel when you stick a hand out the window of a moving car and demonstrates how lift works using a paper airplane. Next, he details the exhaustive testing planes go through, including the “ultimate load test” of the wing, in which a wing is subjected to 1.5 times the force it will ever experience in flight to prove its strength. Bahr then describes how engineers simulate lightning strikes and learn to safely channel their electrical energy through a plane.