Brief Answer:
First 24 hrs is the most important phase..

Detailed Answer:
Hello XXXX, Welcome to HCM..

I've gone through your query and understand your concern..

Now long flights do have their consequences, like this one here, but the health status prior to flight boarding also matters in that case..think about it , was their any thing unusual that you've noticed this time, perhaps some cough/cold ?

First of all , you need to stay well hydrated, drink a lot water as well as lemonades..

Stay away from any kind of alcohol/smoking (if you do..) as they will worsen it even further..

Take Tab VERTIN(BETAHISTINE) 8 mg stat and 4 mg three times a day for next 1-2 days and stay rested at home.. avoid driving..also avoid caffeinated drinks as much as possible..

With all these , you should feel better within a period of time but if symptoms keep on persisting then I'd strongly advice you to get checked up by an ENT specialist for a thorough physical evaluation..

Let me know how you stay in the due course..

Take Care
Kind Regards

---