I've had to change a #2 diaper for DD 2x on the plane - but once she was 3m and the second time 7m - so not quite as wiggly yet!
However, on both occassions I asked the FA, and she advised to change it in the seat- I got all of my "supplies" prepared, and did it super duper quick since she was dressed in an outfit that allowed for quick changes (just in case). I also carry those scented bags to toss the dirty diapers in - so I zipped it in a zip lock, tossed it in the sassy bag - and gave it to the FA. Also, she had given me some air freshener to spray - just in case.
It would certainly be more challenging w/ a 1yo - but isn't something you should worry about.
The other thing that helped me a lot was having my "emergency packs" prepacked. I got quart size ziplocs and put in a diaper, disposable changing pad, a sandwich size ziploc with 4-5 wipes (more than I usually use, but the extra was just for my piece of mind), and one of the sassy toss bags. We kept 2 of these in our bag for on the plane and one in my tiny diaper bag at the parks. This way, we didn't have to dig through everything in a "diaper emergency", and also since I carried my tiny diaper bag on rides, etc we could leave the bigger bag (with change of clothes, etc), under the stroller. For "normal"/planned diaper changes, we just took out of the big bag - but there were a couple of times I was glad I could just 'grab and go'!