Since the external pressure does not remain constant and changes, in any living organism there is a mechanism for adapting to changing external pressure, for some it works better (for healthy people), for others it works worse, including with a long delay. In case of sudden changes in external pressure (it does not matter where it happens - on an airplane, in a pressure chamber, in a diving suit, in a mine, etc.), it "pawns" its ears for the reason that the body has not yet "had time" to adapt so quickly, and therefore, there was "internal tension" in the internal organs, incl. and in the "inner ear", but since the inner ear communicates with the external environment only through the salivary glands and therefore "lays the ears"
To make the pressure in the middle ear equal to atmospheric pressure, you need to make several swallowing movements or open your mouth wide. This increases the lumen of the Eustachian (auditory) tube, which connects the middle ear cavity with the nasopharynx.
That is why flight attendants distribute "takeoff" sweets on airplanes in order to "alleviate" the state of air passengers by initiating the swallowing process, although it is enough to simply "swallow" and without candy.
If that doesn't work, then the second way to get rid of your ear congestion is to blow it out. To do this, close your mouth and pinch your nose with your hands, try to exhale. When you exhale into a pinched nose, excess pressure is created in the larynx, and the air needs to go somewhere - it breaks through the cork.
But if you have a cold or there is an inflammatory process in the ear, then mucus and swelling can narrow or even block the channel, which will prevent the passage of air through the pipe. For this reason, it is undesirable to fly with a stuffy nose and a cold.
If your ears are blocked regularly on the plane, then it is advisable not to sleep during takeoff and landing. If you are on a long flight, ask the flight attendant to wake you up before boarding.