Going through a few aircraft documentaries online, I've noticed the thing that they usually express the fuel quantity in flight hours.
Ex - A 747 burns 4 litres of fuel every second. So with a ton of fuel, it'll stay in air for roughly 3-4 minutes.
Why are flight hours a necessary term while consider fuel quantity? I mean shouldn't they be worried about how much distance they can cover in an emergency to reach an airport, instead of how long they can stay in the air? Seems a question related to endurance but couldn't find any proper explanation