@Peter312
Assuming you have explained the situation to your host and the host is willing to accomodate the change, once you book your flight you can request a change to your reservation and adjust the dates. A few of my international guests also had to request a change due to their flight schedules and in my case, most of these reservations were for over a month, so a few (2~3) days difference was easily accepted and reflected into my calendar.
Like @Linda108 says, there is no such thing as a provisional booking. Either you book a room or you don't. You can send an inquiry to the host to ask questions prior to booking, but reservations/payments from guests are handled by Airbnb. Hosts recieve booking confirmations and payments from Airbnb. So of course, hosts have no idea what goes on between the guest and Airbnb when it comes to credit card charges, payments or cancellations.