Air transport of a MTB with hydraulic brakes
Tires on planes are a problem because they are pressurized above sea level atmospheric pressure. The pressure on a commercial airliner drops below that at sea level, so the pressure difference increases which can exceed the pressure the tire can handle.

Hydraulic brake fluid is not pressurized above sea level atmospheric pressure and the brake system is designed to withstand high internal pressure when the levers are squeezed anyway.