It may have been a while since you boarded a plane, but the next time you do, take note of what side you enter on.
Chances are unless it's a two-seater aircraft, you'll board on the left.
According to some experts, the reason for this practice is twofold.
Writing on popular online forum Quora, Andrew Stagg, a commercial pilot, said the practice initially dated back to ships.
"I believe the reasoning goes back to ships, which have a port (left) and starboard (right) side," he wrote.
"The word starboard comes from 'steer board,' which referred to a board similar to a rudder on the right of the ship.
"The placement of this board required that the port side was the one you would embark and disembark from, so most aeroplane and jetway designers followed the same convention."
Stagg said the universal use of the one side was simply more efficient.
Fellow experts in the discussion said it also helped keep passengers out of the way of the crew.
Krishna Kumar Subramanian, an Aircraft Engineer and system educator wrote: "The cargo doors are on the right; galley servicing is done from the right. To keep the passenger flow away from these activities, boarding and disembarking is from the left," Subramanian said.
"No particular reason why one set of activities is from the left and another from the right except for cargo loading."
This isn't the only feature that has been borrowed from ocean vessels.
A second connection is the colour of an aircraft's wing beacons, which, similar to boats, use red lights on the port side and green for starboard.