I travel the world with my RA and have a few tips for those who might struggle a bit.
MOST IMPORTANT ESSENTIALS TO HAVE WITH YOU ALWAYS
Your meds
Folding cane (just in case)
Comfortable shoes
Passport and no more than two credit/debit cards
e-reader (calming in long lines, easy to hold)
ear plugs (for noisy planes and hotel rooms)
small eye mask for sleeping)
BOOKING FLIGHTS
Allow plenty of time between flights. I cannot stress this enough. You do not ever want to be running for a plane in some monster airport like Chicago, Amsterdam or Heathrow. Use the wait time to shop, to have a decent meal or just enjoy a good book. I always book my flights directly online with the airline I will be using. It is much easier to make changes to tickets that way in case you have an emergency. Online bookings easily let you select your seats and note dietary restrictions as well. Remember that bulkhead seating has more leg room, but also has hard partitions between seats that restrict your ability to wiggle around. Aisle seats are much easier to get in and out and also let you get up and stretch without disturbing anyone.
PACK ONLY COMFORTABLE CLOTHES AND SHOES
I wear business casual pants and long tunic tops in natural fibers that breathe. Think layers. you can layer t-shirts for warmth or layer on a sweater. Add warmth with layers, not with bulky coats. You can always dress up good quality Ts with scarves or jewelry for special events. (my basics are all black and I pick one accent color per trip) Don't waste space on anything you would not normally wear! Pants also let you get away with comfortable shoes (my favorites are Easy Spirit anti-gravity line). Find styles that adjust for when your feet swell. NO ONE wears nylons or pantyhose anymore, even with dresses.
MEDS
Make sure you take a supply that will last your entire trip (you may need your doctor to approve if more than a month). If they need refrigeration pack them with ice packs in an insulated container and check it through in or with your luggage. Carry written prescriptions for emergencies.
LUGGAGE
Take a small carry on with wheels for the plane...do not try to carry luggage on your shoulder or in your hands. Make sure it will fit under the seat in front of you so you don't have to lift. I have food sensitivities (gluten) and always carry enough food to get me to my destination if I can't find things I can eat.
Check your large bags. Airlines are much better about handling baggage then they used to. After years of traveling I have never lost a bag, although twice they didn't make the plane change and I had them sent them on to my hotel (there is no charge for this.)
NAVIGATING THE AIRPORT
Do not hesitate to ask for chair and attendant if you have even the slightest concern about walking to the gate. Remember to tip the attendant, they work for tips which they are not allowed to tell you. They will wheel you right up to the gate and even take you onto the plane if needed.
I always carry a folding cane in my carry on luggage. Most of the time I don't need it, but sometimes towards the end of a trip I am very glad to have it. Also using my cane let's me be first in line for boarding, which reduces the time on my feet. It also gets you offers of help, which is always nice.
Know your home airport well enough to know where you can get a good meal before boarding. Call airport services for help in planning.
PUBLIC TRANSPORTATION
I LOVE using metro systems and trains! That said, be advised there are stairs everywhere in Europe in the stations. Taxis in Europe (especially London) are horrifically expense, but readily available. Pack very lightly if you are going to be using trains and Metro as there are not always elevators available or convenient. Trot out that cane and look helpless and some strong young man or woman will probably give you a hand with your luggage. So, again, allow LOTS of time so you aren't running for a train up or down some long flight of stairs.
Bon voyage!