The esophagus doesn’t just let food, liquids, air drop down into your stomach. It’s a giant muscle that actually squeezes anything you swallow, including air, into a pocket and pushes it down toward the stomach similar to a person squeezing toothpaste out of a tube.
Though, it’s not likely that you swallow air alone but air can get trapped in a liquid gulp that can then be swallowed.
[Animation](https://m.youtube.com/results?search_query=video+of+esophagus+swallow)
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