Opening an airplane door during mid-flight is hindered by several factors. The primary obstacle is the door itself, which is securely locked. However, another crucial consideration that often goes unacknowledged, akin to the Twilight Zone scenario, is the underlying physics at play. To understand this, let's turn to a dependable source—the IMDb Goofs page for the episodes. According to this source, the aircraft that William Shatner's character is depicted to be flying in could either be a twin-engined Convair or a four-engine Douglas DC-6 or DC-7—all of which were designed with pressurization capabilities.
As an airplane ascends to greater altitudes, the external air pressure decreases due to the thinner atmosphere at higher elevations. Consequently, the air becomes less dense, making it harder to breathe since it contains fewer oxygen molecules. This physiological limitation becomes particularly pronounced beyond 18,000 feet above sea level, where our bodies struggle to absorb sufficient oxygen to maintain proper functioning. To mitigate this, airplanes are pressurized to simulate conditions akin to approximately 8,000 feet above sea level. This compromise strikes a balance, reducing oxygen in the blood by a mere 4 percent—insufficient to significantly impair cognitive function.
In contrast, modern commercial airplanes typically cruise at around 36,000 feet above sea level. Without pressurization, these altitudes would induce rapid delirium and unconsciousness in mere seconds. The disparity in pressure between the cabin's interior and the external environment is immense, providing context for the significance of airplane doors in this scenario. Inside the cabin, more than 8 pounds of pressure act upon every square inch of surface area. Given that a standard passenger door measures approximately six feet in height by three and a half feet in width, this results in an overwhelming force of more than 24,000 pounds pressing against the exit. To put this into perspective, even the strongest individual alive can only lift around 1,102 pounds.
The situation would be even more nightmarish at 20,000 feet, though still formidable at 36,000 feet, rendering it virtually impossible for anyone, including someone as formidable as William Shatner's superhuman character, to forcibly open the door. Most passenger doors are engineered with a tapered design, where the inner edge is wider than the outer—a design known as a plug door. This mechanism operates much like a bathtub drain stopper, effectively sealing the opening without the risk of being propelled outward.
Yet, what if a scenario akin to Shatner's extraordinary strength were to transpire? In such a case, the concept of explosive decompression comes into play, and interestingly, the Twilight Zone's portrayal aligns more closely with reality here. In a notable incident aboard Aloha Airlines in 1988, the fuselage tore open at 24,000 feet, resulting in the sudden expulsion of a section of the aircraft's interior, revealing the clear sky where the first-class ceiling had once been. The captain reported that the chief flight attendant was instantly pulled out of the plane through the ruptured gap. Explosive decompression is a rare event, but its effects are substantial.
Whether due to a rupture in the plane's structure or a cracked window, the underlying cause is the pressure differential that generates a vacuum capable of forcefully expelling objects weighing up to a thousand pounds into the sky. This vacuum effect persists until the cabin's internal pressure equilibrates with that of the outside atmosphere.
Given these complexities, Shatner's wise decision to fasten his seatbelt prior to attempting to open the emergency exit is underscored. For those residing outside the realm of the Twilight Zone, the likelihood of successfully opening an airplane door mid-flight remains as slim as spotting a gremlin on the wing.