Tray tables must be in the "upright and locked" position during takeoff and landing primarily to ensure a clear evacuation path. These two phases of flight are the "Critical Eleven Minutes" when the vast majority of aviation incidents occur. An open tray table becomes a physical barrier that could trap you or the passenger next to you in their seat during a chaotic emergency exit. Furthermore, in the event of a sudden, hard deceleration (an aborted takeoff or "hard" landing), a deployed tray table can cause serious internal abdominal injuries as your body is thrown forward. By locking the table, you ensure the seat's structural integrity is at its strongest and that the cabin is free of "projectiles" and obstacles, giving everyone the 90 seconds required by law to evacuate the aircraft safely in a worst-case scenario.