Originally Posted by Italianaviator

Because statistics show that the accident/incident rate dramatically increases after being on duty for more than 16 hours. Reserves can be on duty for 18 with extension. Why chance it and push yourself to work 18 hours when the safest choice would be to wait till the next morning. It's not like these airplanes are 100% trouble free. I sure wouldn't want to have an engine failure at 3am in the morning after working for 18 hours.