Yes. The best place to start is your online itinerary. Make sure to check for the cancellation policy that applies to your reservation. Many reservations already qualify for either free cancellation or no-fee change options. Just sign in to your account and check your itinerary. If you don't have an account, you can use the itinerary or confirmation number in the email you received when you first booked your trip. If you booked a package vacation, you'll have to cancel your lodging and your flight separately.