I have flown the west coast of the USA to Bosnia, to Mexico City and to Ireland. Suggestions I have are:
1.) Do NOT let fibromyalgia be your boss. If you dream of going to see somewhere, DO it.
2) Order your plane tickets early enough to choose your seat if you are flying an airline that allows you to do so. Pay a little extra if needed, but try to get seats with more foot room, (the seats by the bulkhead) if you can. *note that you will have to stow your carry-on in the overhead because there will be no seat in front of you to stow it under. But you are still able to access it.
3.) Bring one of those wrap around neck pillows and a small blanket. Falling asleep on a plane can cause more pain if your head flops down at an unnatural angle, and planes can be cold. That said, they can also be too warm. Wearing layers can be helpful.
4.) When you are awake, make sure to pump your ankles, or better yet, draw the alphabet with each foot every hour or so (and wear support stockings to prevent painful swelling in your lower legs and feet).
5.) I know airplane bathrooms are cramped and somewhat inconvenient, but bite the bullet on that one and make sure you stay well hydrated! The alternative is extra achiness and probably a nasty headache the day of or the next day.
6.) Try to get up and walk up and down the aisle once an hour or so to help keep the stiffness from the long flight to a minimal.

Additional suggestions for your trip:

A) Plan ahead. What is the time difference? Try to spend about two weeks changing your go to bed and get up times to match more closely to what you will be doing where ever it is that you go on your trip.
B) Do your best to take with you whatever comforts you use when you are having a high pain day, such as prescription meds, over the counter oral pain meds or creams such as Voltaren (or the generic equivalent) or Aspercreme with Lidocaine, or pain patches, (pack these items in your carry-On, NOT your checked baggage), a hot water bottle, heating pad (be sure you have the correct electrical adapter for the country you are traveling to), etc.
C) If possible, try to have a relaxing first day. Plan only a very small amount of activity and get some extra rest if you can.
D) Try not to pack the remainder of your trip too full each day. Try to plan for rest breaks during your day.

I hope this is helpful to you! Have fun!

Carolyn i have travelled from Melbourne to england and Europe and from melb to spain just recently and i didn't have a problem. I walked the plane when restless and to ease any pain..don't let fibro kill your dreams..it gave me more reason to do it..

I have Type 2 diabetes as well Fibro and travelled to Pakistan . I live in UK . I found it so much better over there because of the hot country change of weather and dry air unlike UK which is always cold and moist.

Thank you everyone for your advice. I will definitely go now. Thanks very much

Exactly...fibromyalgia is not in charge of our lives, it can be a battle but stay strong