What Would Happen If a Plane Window Cracked Mid-Flight?

As a child, I vividly remember peering out an airplane window on a trip to Seattle. When looking at the bottom of the window, I saw a small hole. I panicked, believing so much as a crack in the window would cause the plane to rip apart and send everyone aboard flying out, falling for miles toward the ground. Fortunately, I was told these holes were normal… However, what would actually happen if an airplane cabin was breached. If a window were to crack, we will assume that the break is not large enough to shatter the glass, but only allow air to escape from the cabin slowly.

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Well fortunately, or unfortunately, we have a few examples of this scenario occurring in real life. For this article, we will look at the infamous Helios Airways Flight 522.

On August 14, 2005, over 100 passengers boarded this plane’s 7,550th flight leaving from Larnaca, Cyprus to Athens. Little did these passengers know that the aircraft’s pressurisation system settings were not properly configured. As the plane took off, the pressure inside slowly decreased. This alerted the pilot, who informed the Helios Operations Center via radio; however, due to symptoms of hypoxia (a lack of air), he was unable to properly follow orders. Soon after, oxygen masks were deployed for passengers and flight attendants. For some reason, the pilot never put on his mask.

The aircraft continued to climb altitude, reaching 34,000 feet on autopilot. Local air traffic control was unable to contact the pilot or crew. Without the direction of the captain, the plane continued on autopilot and flew over Athens. This alerted the flight attendants and prompted Andreas Prodromou, an attendant, to investigate the cockpit. He found the pilot unconscious due to a lack of oxygen. He then attempted to fly the plane. At this point, the engines had already begun to flame out without fuel. Because of the above factors, along with his inexperience at flying, the plane eventually crashed killing all passengers and crew.

In short, in the event of cracked window during flight, we can expect:
• Gradual cabin pressure decrease, leading to airmask deployment
• Alarms prompting pilots to land the plane
• Alerts to air traffic control to address the situation

Fortunately, most flights in this scenario would likely have a conscious pilot who can work with air traffic control to promptly land the plane. Although the flight would likely be terrifying, it is not necessarily life threatening.

By the way, if you were wondering the reason for the tiny holes on plane windows, they are actually in place to equalize the pressure between the cabin and the space between the window panes to prevent cracking/breaking!