У стойки регистрации я показал паспорт и посадочный талон.

At the check-in desk, I showed my passport and boarding pass.

Breakdown of У стойки регистрации я показал паспорт и посадочный талон.

• я: I
• и: and
• у: at
• паспорт: the passport

Questions & Answers about У стойки регистрации я показал паспорт и посадочный талон.

Why is it у стойки регистрации? What does у mean here?

Here у means by, at, near.

So у стойки регистрации means at the check-in counter / by the check-in desk.

A useful pattern is:

• у + genitive = at / by / near someone or something

Examples:

• у окна = by the window
• у двери = by the door
• у входа = by the entrance

So this phrase is not literally saying inside the counter area, but at that location.

Why is стойки in the form стойки instead of стойка?

Because the preposition у requires the genitive case.

The dictionary form is:

• стойка = counter, stand, desk

After у, it changes to genitive singular:

• стойка → стойки

So:

• у стойки = at the counter

This is a very common case pattern in Russian: the preposition determines the case.

Why is it стойки регистрации? Why is регистрации also changed?