Rotors & Pedals off.
Bars off
Seat down
Pad Spacers fitted
Make sure you have the tools to reattach.
Helmet as hand luggage, if you have the weight pedals and tools inside a camelback.
Sometimes I’ve used a sheet to wrap the bike inside the bag if there is some loose stuff in there.
Haul it by the lower handle.
If you are touring round then you can leave the bars on and just zip up to the bars and poke one end out.
Put something on one of the handles so you know it’s yours if it’s a popular bike flight.
When asked there is just a bike and packing stuff in there, and yes I did let the tyres down.