Pinch your nose and take a few sips of water. Swallowing helps pull the Eustachian tubes open.
If the Valsalva maneuver doesn't work, try this: clogged ears after flying
While it usually goes away on its own, that muffled hearing and pressure can turn a great trip into a frustrating one. Here is why it happens and, more importantly, how to get your ears popping again safely. Pinch your nose and take a few sips of water