Hello Alicia :)
Horses are placed in boxes, they have access to water and hay, and will be resupplied if it's a long flight.
Some grooms are flying with the horses but not all of them, in any case there're professionals on the plane to check on the horses!
Hope it helped :)
Hi Alicia, some of my horses have traveled by plane so I am a bit used to it. You need some documentation (vaccination schedules, health certificates...). Each horse is in his compartment, it looks like the inside of a horse trailer. They cannot move from their standing stall but they have hay and water during all the flight. Professional qualified flying grooms travel with the horses on the flight. Some even spend time with the horse to avoid stress. According the country your horse is going, there can be a an isolation period. Here is a movie's link on the subject: https://www.youtube.com/watch?v=1l4x1NYirSw