When planning air travel with a broken arm, confirm with both a doctor and the airline that it's safe, and ask about any additional requirements or considerations. Possible side effects may occur with flying, and the airline may have to make certain accommodations.
If the fracture is recent, swelling is common and blood clots may occur when flying for more than four hours. Moving around frequently throughout the flight helps reduce these risks.
Coordinate ahead of time with the airline to ensure having a seat with extra room, such as one near the bulkhead. The seat should not be in an emergency row, and an aisle seat may be more appropriate if regular access to the lavatory is needed.
Plan for additional time to get through ticketing and security in the airport. Any prescription pain medication should be packed in the original container and clearly labeled. Inquire at security about getting through the metal detectors if there's any metal in the cast or sling apparatus, and be prepared for security to inspect the cast for explosives. The process is quick and painless, but a separate inspection room may be requested for privacy. Inquire with the airline about boarding the plane early, and ask the attendants for assistance with any carry-on luggage.