Buzz
While some passengers may be too scared or sedated to notice, others might question why airplane windows differ from those of homes, which are usually rectangular, or car windows, which often have an angled, mostly rectangular shape. Why don’t airplanes follow this pattern?
It’s not about looks. Airplanes once featured square windows. However, they were responsible for crashes.
As commercial airlines advanced with larger and faster jets in the 1950s, some planes would tragically break apart mid-flight. Two de Havilland Comets fell apart within months of each other in 1954, resulting in 56 lives lost. Investigations revealed the issue stemmed from the sharp corners of square windows, which concentrated stress from a pressurized cabin and were vulnerable to breaking. A Royal Aircraft Establishment test showed that the corners of these windows absorbed up to 70 percent of the airplane’s stress.
Circular windows quickly became the go-to design in passenger planes because they help distribute pressure more effectively. For every circular window, there are actually three layers at work: one to handle the pressure, a secondary one to act as a backup in case the first fails—which doesn’t happen often—and a final 'scratcher' pane facing the passenger, allowing you to smudge it to your heart’s content.
That small hole at the bottom? It's there to ensure the pressure is primarily absorbed by the main pane, leaving the backup pane intact for emergencies, just as it was intended.
Mystery resolved.
