Rounded windows help distribute air pressure evenly across the surface, minimizing stress on the fuselage. In contrast, square windows have sharp corners, which concentrate stress and increase the risk of cracks.
After early aircraft disasters like the de Havilland Comet crashes in the 1950s (due to square windows), rounded windows were introduced as a safer design to prevent similar accidents.
Rounded shapes are naturally more resistant to the fluctuating pressure changes experienced during takeoff, cruising at high altitudes, and landing, enhancing the durability of the aeroplane’s structure.
Smooth, rounded shapes cause less drag than angular designs, contributing slightly to the aircraft's overall aerodynamic efficiency.
Planes need to maintain internal pressure at high altitudes, and rounded windows help the aircraft handle the stress from cabin pressurization more effectively than square ones.
Rounded windows provide a more pleasant view and reduce glare and distortion compared to square windows, enhancing the overall passenger experience.