Hi & Welcome to HCM. I appreciate your concern for your son s anticipated vomiting during air travel. It appears that he is having some sort of motion sickness which occurs during travelling by car, bus, plane, etc. Ondem is not safe for the treatment of motion sickness in children. Antihistamines (like Cinnarizine, Cyclizine, Diphenhydrinate or Promethazine) are the most frequently used and widely available medications for motion sickness. The are available for oral administration and suppository through the rectum. Since your son has a tendency to vomit you may either give the above medications either along with fruit juice or rectal suppository can an alternate and effective choice if he continues to vomit. Hope this answers your query.