Hello there @Teresa25, sorry to respond so close to your flight but I had a look around the forum to see what others have shared previously about flying with Myeloproliferative neoplasms ('MPN') like Essential thrombocythemia ('ET') and Myelofibrosis (‘MF’), hope you don’t mind.
There’s this thread, where Nurse @Heidi_BloodCancerUK suggests “laps of the plane aisles and your foot/ankle exercises whilst sitting”: Air travel with ET
Here’s a great Blood Cancer UK post about travelling with blood cancer that has loads of useful tips: Blood cancer and travel: your guide | Blood Cancer UK
Personally I’d wear compression socks too just to add another layer of support (literally!). Have a great holiday @Teresa25, do let us know how it goes!