Block time
Block time is the elapsed time from the moment the aircraft first moves under its own power, when the chocks or blocks are pulled, to the moment it comes to a stop at its destination. It includes taxiing and any waiting on the ground with engines running, so it is longer than airborne flight time by 10–25 minutes on a typical sector and much more at congested airports like Teterboro or Heathrow. Most charter operators bill by block time, so a quote based on flight time can understate the real cost; ask which the operator uses and, if it is block, whether there is a cap for taxi delays beyond your control.