To add a bit more nuance here: Hydro probably isn't the best choice for travel bikes. I had problems with Apex1 needing a bleed after air travel, probably due to pressure changes. Probably even more faff for breakaway or SS coupling style frames, where you cannot break the hydraulic line easily.
brake pad spacer inbetween the pads before the flight.
Have flown with mountain bikes and never had an issue with the brakes due to flying.
Plenty folk taking bikes on flights multiple times a year so I dont think it causes problems.
To add a bit more nuance here: Hydro probably isn't the best choice for travel bikes. I had problems with Apex1 needing a bleed after air travel, probably due to pressure changes. Probably even more faff for breakaway or SS coupling style frames, where you cannot break the hydraulic line easily.