In response to Hurricand Irma, here are the published rebooking policies by airline. Given the very fluid situation and unknown extent of disruption both the dates of flights eligible for proactive rebooking may change and the date up to which you can rebook may change (as they have already done) in the coming days.
Please note that if you have booked a tour package via a travel agent, the options below may not apply and you should contact your travel agent directly.
It is also worth noting that if you are due to fly via Miami on BA or Virgin to another destination in the Americas it is worth exploring an alternative routing via the hubs of their partner airlines.
BA has extensive codeshares with Iberia from Madrid and American Airlines from hubs such as Dallas Forth Worth and New York JFK. Virgin also has extensive codeshares with Delta from hubs such as Atlanta and New York JFK.
If your flight is cancelled you will be entitled to a full refund and reimbursement of reasonable incidental expenses. If your flight is operating but you choose to rebook to an alternative date/destination any consequential costs may not be met by the airline.
It’s also worth noting that many smaller hotels / guest houses in Florida have already closed for business until next week. Larger properties have also waived change / cancellation fees.