The Aerial Maps can not be downloaded for offline use as you can with your regular downloads on either the iPad or the iPhone. This means the Aerial Maps will not be available to you in flight.
We have a workaround that may work for your needs. Just before your flight, while connected to the internet, view the Aerial Map you want to have available to you in flight. be sure to zoom in and out on the areas you need as well as pan around the map.
The Aerial Maps you view will be saved into ForeFlight Mobile's temporary storage (Cache). This will allow you to access those Aerial Maps while in flight provided the cache is not cleared or requested for other system resources.
If you try this workaround, please know that if you pan or zoom to an area that you didn't preview before your flight, there won't be any Aerial Maps visible for those areas or zoom levels.