Re: Too many Braxton Hicks at week 25? Need your advice
My doc told me to tell them if I had more than 4 BH in an hour... I'm 24 weeks.
As for the trip, my doc said "no planes, trains, or automobiles" after 32 weeks... meaning that regardless of the method of travel, don't go more than a few hours from home after that point. But, I haven't been given any restrictions like you have. I, too, am at risk for pre-term labor due to a large fibroid (10 cm), and am having bi-weekly transvaginal ultrasounds to measure cervical length.
Unless you bought refundable tix you are not going to get a refund, though usually you can use the value of the tix towards another flight (minus a fee) within a year. Notes from doctors don't get you very far with an airline (unless it's to carry a "banned" liquid or gel for medical needs... ha!). I would definitely stay home and protect my baby, as hard as that may be. Hopefully you can watch a video of the ceremony and reception and maybe call and talk to your sister the day of the event... I'm sure she would understand.
Also, my perinatalogist told me that ibuprofen is ok to take until 32 weeks, but not after that. He told me to take it for back aches and for any pain the fibroid causes me.