I wear all the gear all of the time. I don't trust other road users. There are plenty of moron/ drunk/ drugged cage drivers trying to take you out. And animals, pedestrians etc. And rider error. No-one is infaliable.
I try to plan my riding not to ride somewhere if the weather isn't to my liking.
Because of weight restrictions, I wear my MX boots onto the aeroplane and carry my helmet in a helmet bag. No-one at the airport seems to care about your bike jacket as long as everything is permitted from a security point of view. I recall weighing my jacket once and it came in at 25kg! Knee braces and clothes in the arms, body armour laced into the jacket with zip ties, all the pockets full of my heaviest electronics. Yes, you'll spend time at security while they search everything Just get there early in plenty of time.
At the boarding gate, be able to carry your heavy jacket over your shoulder "casually" (you're clearly unable to wear it

), maybe draped over your helmet too. Use your body to obscure it's size depending on where the boarding gate staff are standing/ looking. Always be friendly (distraction technique

), have your passport/boarding pass ready etc.
On the flight, the boots go in the overhead locker or underneath the seat in front. Sandals/ flipflops/ light weigh shoes go on my feet. To walk off the plane, I carry a length of webbing and tie the boots together so I can carry them over the other shoulder not carrying the jacket.
If my luggage/ bike clothes are only going one way (e.g. I'm repatriating a bike back to home, as I did recently, bike was parked over the winter in the Caucuses and I rode it back to Europe), I put hold luggage in a "Chinese laundry bag" wrapped in cling film for extra security/sturdiness, that can be binned at the destination city/ airport.