If mum did not have an isle seat and you did. You should not swap. She could have paid for a seat next to her child and chose not to. Letting you do it. I would never give up my isle seat unless I was getting another isle seat. Remember the stewardess could also work something out.
“I would never give up my isle seat unless I was getting another isle seat.”
I wouldn’t, either, again. I did that once between Hawaii and LAX just to be nice to a honeymooning couple so the could sit together. The lady next to me smelled SO BAD ... for 5.5 hours. Never again.