Ever wondered why flight attendants insist on you putting your seat back in its original position upon takeoff and landing? It's just a few inches of difference, so it doesn't seem like an incredibly imperative safety measure-- but it is.
The law is set by the Federal Aviation Administration, and, according to Travel and Leisure, it was put in place for two primary reasons: "it makes it easier to evacuate the plane in the case of an emergency and it can help limit injuries."
A study recently conducted by Boeing found that 58% of fatal plane accidents occur during takeoff or landing, and having the seats readjusted to their upright positions ensures that there's one less obstacle if passengers have to evacuate the plane.
Travel and Leisure also notes that having seats "upright during take-off and landing also cuts the chances that your face will slam into the seat back in front of you during a bumpy landing. It's not just a consideration for the person behind you, either. If your seat is reclined, you're also at a greater risk of head injury, because your head would have further to travel before impact, generating more force, and risking a graver injury."
The bottom line is, put your seat up when the flight attendant tells you to. A few more minutes of relaxation isn't worth the risk.