I need advice about air travel with two cats, any suggestions?

I am moving across the country and will be bringing my two cats. They are 11 years old and I think the girl will be OK, but the boy is very hard to even get to the vet. I am BEYOND nervous but have no other option. I have booked them to come on board with me & they will be under the seats in front of me for the 7 hour flight. My bigger fear right now is having to remove them from their carriers to go through security – I’m worried I would be able to get the boy out!! Have any of you traveled with cats? Do you have an suggestions/advice? Anything to put my mind at ease a little is greatly appreciated!