Waiting lists
Ask to be told when a booked slot comes free.
Join. When an aircraft is booked for the time you want, choose Join the waiting list. You can wait for that aircraft or for any aircraft of the same type.
An offer. When someone cancels, the first person in line is offered the slot and held it while they decide. You are told by Inbox and email. Choose Answer to accept or decline. If you accept it becomes your booking and you get the usual confirmation. If you decline or the time runs out, it goes to the next person.
Leave. You can leave the list at any time from My Bookings.
Switching it on. An administrator turns on Waiting lists in Settings > Modules and sets how long an offer is held.