Deducing from FAR 121.471, a pilot can log just shy of 8 hours of flight time while being on duty for a maximum of 16 hours straight as long as he/she gets 9 hours of rest. Most airlines institute a 14-hour duty day limitation, which can be extended to 16 hours due to inclement weather and mechanical delays. But in no instance shall a crew take a flight knowing well that they would violate the 16 hour regulation. At that point, your pilots usually advise you that they will need to re-crew the aircraft and flight in order to get you to your destination.