This would go in stages.
First follow Tymoteusz Paul's answer. Just because they picked you to do this trip doesn't mean it has to be you. Your boss may have two people who he thought equally suitable to do this trip and picked you since he wasn't aware of the problem. If you tell him, he may say "no problem, I'll ask Joe to do this". Joe might not be quite as suitable as you are, and the boss might push back asking "are you sure you can't do this job? " and give in if you make clear enough that it is a real problem for you.
If the boss cannot be convinced then you need to see a doctor, and get documentation that says either you cannot do this journey, or that it would be an extraordinary hardship for you. And that documentation goes to your boss and/or to HR. That and expressing strongly that you can't go on that trip, that you will likely have to interrupt your journey or will not be able to do the job should get you out of it.
If the company is unreasonable at this point (or for some reason there is no choice because you are the only one who can do the job, and it absolutely must be done at the other company and can't be done near home):
There are three choices. You go on the trip. You don't go and stay with the company. You don't go and don't stay with the company. Up to the company whether they prefer (2) or (3). And up to the company to convince you to go. Everyone should investigate how to best cope with it. Maybe long breaks between flights. Good noise cancelling head phones. A quieter flight. A seat in a better position. Possibly contacting the airline, they would have more experience with this.