Brief Answer: It is because of blockage of eustachian tube. Detailed Answer: Hello, Welcome to health care magic. It seems from the history that you feel crackling sound when you swallow. It is because of blockage of eustachian tube, a tube connecting ear with nose and it is essential for equalizing the pressure and maintaining it in the ear. This tube gets blocked because of collection of secretions in ear or because of cold and nasal discharge. Every time as you swallow the muscles surrounding the tube contract resulting in cracking sound. This is treated by decongestant drugs if it is problematic. Since you have mentioned that you will be using flight to travel, while flying because of change in air pressure a blocked eustachian tube can lead to blockage of ear and pain hence I advice you to consult ENT doctor once before flying for treatment of this condition to prevent inconvenience during flight journey. Hope I have answered your query. Thank you

---