I prepare for vacation trips in the same way the military prepares for a hostile invasion on enemy shores. To be fair, I no longer travel much and have never traveled by plane, but when I was much younger my parents would do camping trips with me and my older sisters , one of whom also has SMA.

1) Make a list. Think of everything you need, especially medical provisions and make a list. Don't assume you can easily get something you need where you are going.
2) Accessible means different things to different people. Just because a hotel claims a room is accessible, don't believe them. Interrogate the hotel manager like a CSI crime scene detective questions a suspect they know is lying .
3) Assume that everything hotel tells you about room is a lie...have a plan B.
4) Don't assume that just because you reserved an accessible room ahead of time that this is the room you will get. Some hotels give accessible rooms first come, first serve...even if reserved the room.
5) No two toilets are the same height. If need a bathroom chair, either bring McGuiver with you or have a plan.
6) It is easy to forget wheelchair chargers ...don't...just...don't.. Pack it first.
7) This is dumb...but has to be said . Power wheelchairs are not ATVs. Regardless of how often driven through mud or whatever the wheelchair salesperson said about the durability of your wheelchair ...wheelchairs do not like sand or water...especially salt water. So unless you want a $25,000 + bill for a new wheelchair ....don't drive a non beach designed power wheelchair along the surf of a beach. I witnessed this done...did not go well.
8) Google search a couple dozen restaurants in whatever area visiting . Look at photos to help judge accessibility. Restaurants in tourist areas are rarely accessible ...will always say they are if call them. Accessible to many restaurants is a sixteen year old waiter who lifts weights in his parents garage and thinks can lift a 400 pound expensive wheelchair up a flight of stairs .Tables are often places so close together you can smell the garlic breathe of the guy at the farthest table. Be prepared to quickly call ahead to other nearby restaurants or you may end up at a McDonald's drive thru at midnight .
9) Tourist destination sites are typically similar to restaurants with the exception that park rangers are very helpful . Park Rangers don't want to lug a 400 pound wheelchair to rescue someone so they are much more honest about safe areas to travel with wheelchair. There are still helpful travel brochures too.
10) Try something new...even if scares you a bit. My best travel memory was parasailing over lake George in New York . They landed me right back in my wheelchair . Travel does mean taking risk and having new experiences. Plan for what you can, roll with what you can't .

Do your research on accessible transportation at your location!

Pack all essentials (wheelchair charger, continence care, medications etc.) in your carry on!

Contact the airline ahead of time to outline your needs!

Check your airlines policy on repairing damaged mobility devices!

Check out beach wheelchairs if you want to get into the water!