Kat, you will most likely be fine with your dosing prior. If you have MM, take a SPUT with you to the airport. You can suck on it for a long time when you get on the plane. If you are concerned about traveling with one, you are not when it is in your mouth. That, along with caffeine in any form should take up any slack. No drinking booze.
I suggest having coffee before take off. Having energy shots at hand when boarding!
I was terrified to attend the Dallas conference because I had to fly. Well, they really meant it when they stated 'We are only looking for explosives'. There was other stuff there if they were 'looking' for it. They were not. They did however have me open the bag to show them what was making the funny pics on x-ray! It was my Clustermask and regulator! LOL.
You may not want to take any alternatives and I do understand that. Do your preventative busts before! If it goes south while you are there, go to the firestation with your mask in hand and ask for some O2? It works many places in the states, so I would try for that solution there first. We all know how bad the ER can be, so that often ranks second.
That 'on landing' headache is from the increase in air pressure. I get a hit with the reduction in pressure. So, take off. The plane does not have the same atmospheric pressure as we have at sea level when it is airborne, it is lower. Like a low pressure front moving into your area. If high pressure is a trigger for you, then yes, landing would be the time to be concerned.
Have your preparations in order before and your 'prevents' packed for the trip. Slap on a smile and head out! Then report back here, ok?