They filled the vacancy by appointment.

I'm sorry we couldn't get you a seat on first class.

There were a lot of empty seats the day I went.

This morning the train was so crowded that I couldn't find a vacant seat and had to stand the whole way.

Are seats available?

There is no sense in standing when there are seats available.

There wasn't a single vacant seat in the hall.

Since there was no vacant seat on the bus, I stood the whole way.

There being no vacant seats on the bus, I was kept standing all the way to the station.

There being no vacant seat in the bus, I kept on standing.

The post will fall vacant.

Are there still some empty seats?

The buses ran back and forth almost empty.