On the plane, the guy sitting behind me suddenly put his dirty foot right on my armrest — and I had to teach him a lesson in manners 

The plane had just reached cruising altitude. I was settled by the window, had my headphones on, and opened my book. Everything was calm until something cold and unpleasant touched my armrest.

I slowly turned around — and froze. On my armrest lay a dirty foot in what used to be a white sock, now gray and worn.

— Hey! — I exclaimed, outraged. — What on earth is this?!

The guy behind me didn’t even bother to move his foot. Without lifting his eyes from his magazine, he lazily said,
— Relax, sweetheart. It’s just a bit tight here.

— Tight? That’s no excuse to stick your feet wherever you want! — I snapped, feeling anger rising.

He finally looked at me, smirked, and said without moving his foot,
— If you don’t like it, go sit in business class. I heard there’s more room there.

A few passengers turned their heads. I could feel my face heating up.
— Want me to bring you a pillow too? Or maybe give you a pedicure?

He snorted.
— You’re too uptight. Relax, I’m not hurting anyone.

— No, just my armrest — with your sock, — I muttered through my teeth. — Great start to the flight.

I took a deep breath and decided not to make a scene. Instead, I came up with a lesson in manners he’d never forget  Continued in the first comment 

I asked the flight attendant for some tea — hot, black, no sugar.

A few minutes later, the cup was on my tray. Again, I felt his heel brushing against my elbow.

I slowly turned, smiled, and said softly,
— You know, you were right… we really should relax.

Then, as if by accident, I tipped the cup of hot tea right onto his foot.

— Aaaah! Are you crazy?! — he yelled, jerking his leg back.

— Oh, I’m so sorry, — I said with the most innocent expression. — It’s just so tight here… you understand, right?

The passengers tried to hide their smiles. Even the flight attendant, walking by, gave me a discreet wink.

For the rest of the flight, the guy sat quietly, both feet neatly tucked under his seat.
Lesson in manners — learned.