I got home last night from an RTW with my family, including my mom, who is 80. Understanding there is a big difference between 80 and 91, if she decides to make the trip you should consider shorter daylight hops with at least one night at each stopover point to catch up on time zone changes. If you’re in a premium cabin and use a good hotel, the ground experience should not be a problem. You’ll be off the plane early and there will be a wheelchair attendant on the jet bridge to whisk you to customs, where they’ll take you through the special assistance/diplomatic line so the attendant doesn’t have to wait. Arrange for a limo transfer with a good hotel and there will be someone waiting outside customs to take care of luggage and to get you to the car. After a long flight arriving in a foreign city, it saves tremendous wear and tear not to have to bother with taxis or hotel buses.

You should select seats on the plane close to the washroom so she doesn’t have far to walk and can see if there are others waiting before she gets up from her seat. If you’re flying on a 747, you may want to choose main deck rather than upper deck seating so she doesn’t have to climb stairs to get to her seat. For what it’s worth, my mom doesn’t care much for flatbeds or “suites”. I couldn’t get her to let them make her seat up as a bed (our long hauls were on CX, EK and EY). She found it more comfortable to be able to change the angle of the seatback and footrest. She doesn’t like the isolation of “suites”, and wants to be able to chat easily with a family member in an adjoining seat.