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You may have flown abroad hundreds of times, revelling with your novelty hat on and half cut from drinks at the airport bar before you even get on the plane. But in your ignorance - or drunken state - you may have never noticed that you always board the aircraft from the left-hand side. Mindblowing, right?
Now experts on the question-and-answer site Quora have revealed that the convention may date back hundreds of years due to the way that people traditionally boarded boats.
"Early airports were set up so that aircraft could taxi in front of the terminal and stop to discharge passengers," wrote a former US air force pilot on the site.
"It was useful for the pilot to be able to judge wing clearance from the terminal building and to put the aircraft door in front of the terminal doors. Some early transports had right-side doors into the passenger cabin, but the logic of the pilot's field of view prevailed."
The pilot noted that at some airports stairs might be placed elsewhere on the plane, but loading/unloading is always on the same side to avoid passengers wandering around a busy parking ramp.
The pilot explained that passenger movement is often kept on the opposite of the side of the plane from fuelling and unloading/loading baggage for safety reasons.
However, Andrew Stagg, calling himself a commercial pilot, had a different explanation, saying the tradition dated back to naval history.
"I believe the reasoning goes back to ships, which have a port (left) and starboard (right) side," Stagg wrote. "The port side was the one you would embark and disembark from, so most airplane and jetway designers followed the same convention.
"While most larger transport category aircraft have two front and two rear exits, the placement of catering trucks and baggage loading equipment on the right makes using the right doors impractical."
People boarding the Titanic in 1997's Titanic... On the left hand side. Credit: PA
This explanation was backed up by Adrian Young, a senior aviation consultant at To70, who said that the vast majority of modern aircraft board/deplane on the left hand side and are serviced on the right.
"This is something that has developed over the years," Young told the Independent.
"Some people point to the fact that on [ocean] liners passengers left from the port side. Until the 1960s, prior to the construction of jet bridges, aeroplanes would often park with close to and parallel to the terminal.
"With the captain sitting on the left and often the pilot tasked with taxi duties, parking with the left side closest to the terminal is easiest to judge for the captain. Jets like the DC-8 even parked like this at Schiphol when the first jet bridges were installed."
Young explained that aeroplanes have now standardised this historic habit, with all fuelling, loading/unloading and most cleaning and catering vehicles parking on the right hand side.
So next time you're flying abroad on holiday, have a look to see which side you're getting on. If you're still sober enough to see, that is.
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