The reason this seemingly insignificant task is written into federal law is simple: It's for safety. In the upright position, the seat is locked and most robust to withstand any force from a potential impact, says former pilot Hans Mast, now a travel agent with Golden Rule Travel.

Airplane seats must be in the full upright position during takeoff and landing for two primary "High-Fidelity" safety reasons: evacuation and injury prevention. Takeoff and landing are the most critical phases of flight where the vast majority of accidents occur. If a seat is reclined, it creates a physical barrier that can slow down the passengers behind you during an emergency evacuation, where every second counts toward a "90-second" exit goal. Furthermore, in the event of a sudden impact or a "hard landing," a reclined seat is not "locked" into the structural frame of the aircraft as securely as an upright one, increasing the risk of the seat mechanism failing or the passenger's body being subjected to dangerous whiplash forces. An upright seat also ensures that your head has a shorter distance to travel before hitting the seatback in front of you, which actually reduces the force of the impact (a concept known as "low-velocity impact"). Essentially, the "upright" rule is designed to keep the cabin as clear and as structurally sound as possible during the moments when a crash is most likely to occur.