We have a nice portable changing pad with pockets in it. It folds up nicely with a few diapers and a small plastic wipe case.

Usually, there are two of us and we put the pad on the top of the toilet. One of us will help hold while the other changes. Not too difficult. After we get her out of their we'll wipe down her hands/feet as well. It seems like every toilet is unique in its configuration so you really can't have a plan until you see your options.

The FA's are generally great about helping find a spot. We've used the floor in the front and rear galleys a few times with FA assistance in blocking people.

I think a real key to travelling with a baby is to make sure you have time and stay calm. My daughter senses the airport and airline chaos and I think she remains calm because we don't get agitated.