A method for generating a flight route includes receiving an unconfirmed flight route of a drone, displaying a visually observable area based on a position of an observer who visually observes the drone, confirming, if the unconfirmed flight route is entirely included in the visually observable area, the unconfirmed flight route as a confirmed flight route, and displaying, if at least a part of the unconfirmed flight route is not included in the visually observable area, a warning message indicating that the unconfirmed flight route is not confirmed.