You can certainly purchase the travel insurance right away. You should however include the cost of your airline tickets in the trip cost. If you can find out what the price of the tickets will be before purchasing them, you can include that amount in the total trip cost. If not, an estimate will have to do. Otherwise, buy the policy now with the costs expended to date and contact us at email@example.com when you make your other arrangements and we will have the policy corrected to reflect the change. If there is any additional premium as a result of the change, it will be charged at that time. Be sure you do this within the 7 – 21 day purchase requirement (depends on company) in order to comply with the pre-existing condition waiver requirements.