Depends on Hunter type, F6/9 or T7(smaller engine),then on aircraft tank fit,internals +2 x100 gal/4 x100g/or 2x230 /or 2x230+2x100.Then depends on how far you want to go,preferably high,then remain orbiting,or are you following,possibly, What are the upper winds,what is your diversion options,ie down-route,or RTB..?A C130 will cruise at about 300-320kts max,and fuel for about 7-8 hrs internal appx..A Hunter in max fit will have about 8200 lbs fuel and at low level will use about 4500lbs/hr,reducing to about 2500 l/hr at 30000ft.So if it`s a `chase` and then RTB at high level ,I would reckon airborne for about 2.5 hrs max.
I`m sure a Hunter expert will be along shortly to correct my `guesstimate`....!!