Travel for senior citizens can also be daunting if they have problems with hearing or use a hearing aid. Airports are VERY noisy and the myriad sounds are distorted anyway. For a senior citizen traveling and attempting to understand announcements via loud speakers, or even a verbal answer to a question can be very disconcerting.
And bathrooms can be a major road block in travel for senior citizens. Sometimes, elderly people have to go immediately. Long lines in the airport restrooms or waiting for their turn on the airplane can pose quite a difficulty. Often they will need access to grab bars and a raised seat, or they may not be physically able to stand up again.
The small spaces allotted on airplanes may make it exceedingly difficult to maneuver with a purse, and a cane. Not to mention being intimidated by the new "gadgetry" -- the locks and handles, and faucets and flushers and towels are all so radically different. If you have even a little trouble seeing it could be more than a little embarrassing to get locked in (or forget to lock a door), not to mention not be able to figure out how to flush.
With time being totally fluid during airline travel, make sure your folks have a contingency plan for meals and medication. Don't let Dad say he'll just eat when they arrive if his medication must be taken on schedule. Many medications must be taken on strict schedules, and before or after a meal or with food.
Diabetics need to account for meals and insulin. Work with them to coordinate medication and meal times with scheduled travel times, and have alternate plans worked out for delays. Having to come up with a new plan on the spot may not always be possible if food courts are far away or closed. Food and drinks can be carried on board the plane... drinks just have to be purchased after the security check points.
Make sure they take the medications they will need for a couple of days with them on board and not packed away in a suitcase. Also, make sure they have a list of all the medications and medical cards, their home doctors and drug store phone numbers in case there is an emergency need for replacements.
Now you can see why it's not a good idea to "surprise them" with a trip. Sure, travel for senior citizens is more than possible. It's even possible for them to travel with their beloved pet. But you've got to have the time and patience to listen to their concerns and talk about any potential problems. Work with your folks and the airlines, ahead of time, to make sure their trip is safe and enjoyable.