On a JFK-TLV flight I had an aisle EC seat in the middle section and the seat next to me, a middle seat, was empty. It was the only empty seat on the entire packed plane. Lucked out big time.

For whatever reason at least five people in the regular econ section, incuding a lady with her screaming baby, asked to sit in that seat. The FA told every one of them, "That's Economy Comfort. You have to pay extra to sit there." Everyone backed down. Kudos to the FA for enforcing the seat assignments!