The armrest of the aisle seat might seem like it can’t be raised, but appearances can be deceiving. Many aisle seats have a hidden button or lever that will let you raise the armrest.
This tip comes in handy if you want to spread out more, although some flight attendants might tell you to lower it back. It can also make it easier to get out of the seat. I like to get up and take a walk, not far to go, but stretching the legs on long flights is good.
A few years ago I saw a person a few rows ahead of me raise the armrest on their aisle seat. I had to work out how it was done, so I watched next time they got up. They appeared to reach under the armrest near to the hinge, of course I had to try this. There was a small lever in a recess just in front of the hinge, I moved it forward then simply lifted the armrest out of the way.. No more ducking! Simply raise the armrest, then stand up while you slide off your seat into the aisle.
There are a few planes that do not have movable aisle armrests. However, most of them have a small lever or button on the underside of the armrest, near the hinge. Pushing or sliding this lever will release the hinge lock, allowing you to raise the armrest.
So maybe you can be a bit more comfortable on your next cramped flight.