I used to suffer with bad coughs all the time (I don’t smoke) and they would last for ages. Once I had this cough and it wouldn’t go and I was flying to America the next week. My friend told me to go to the doctors as they had given her something to stop her coughing once.. So I went to my doctors to ask her if there was anything at all I could take to stop it as it would annoy all the passengers. She gave me a prescription for a syrup medication. It came in a brown bottle and OMG it really worked and stopped me coughing.. But I’m sorry it was about 20 years ago now and so I cant remember the name of it… I seem to remember it was a surgery syrup.
I don’t know if they still do it but why not go to the doctors and ask.
xx