I had to cancel a flight just last week due to illness. We were flying on Southwest. They still have their policy of applying the funds towards a future flight with no penalties. You can cancel for any reason and this would apply. I also asked about whether or not I could reschedule for the next day. She asked if I had been to the Dr. I replied that I would probably be going in later that day. She gave me the customer service # and said that with a Dr's excuse I might be able to reschedule for the next day with no fare increase or penalty depending on availability. The only thing I would lose out on would be the double credit for booking online. I love Southwest! Unfortunately I was not well enough to reschedule.