(WYTV) — Time to board your flight — have you ever wondered why you always get on board on the left side or the port side of the aircraft?

The cockpit is always to your left as you step on board, and you turn right to walk down the length of the plane and find your seat.

Here’s one big reason: the ground crews are working on the right side of the plane refueling and loading and unloading luggage. They can work uninterrupted if you’re using the left side to board and leave.

Here’s another reason: the pilot sits on the left side of the cockpit and it makes sense for his or her side to be closest to the terminal. The pilot can judge the distance between the tip of the wing and the building most accurately to offload passengers and take on new ones.

And one more reason, a maritime practice: ships usually boarded the same way, on the port side. The other side, the starboard side, had gear for steering that could get in the way of docking. The airlines kept the tradition.