T. A. Gardner wrote: Even if the supplies were available and plentiful, the lack of operational aircraft (rates ran at 25% or less typically), the inability to fly many days, and the almost appalling condition of the airfields and support services at both ends pretty much doomed the effort.
This is true, but, OTOH, one can ask the question that, if more aircraft would be operational,there would be more supplies available . The point that when a build-up was organised by Milch, (=more operational aircraft) this did not result in the transport of more supplies,is suggesting that the original problem was with the number of available supplies,for which the LW could not be blamed,and that the LW only was increasing the problem .
The following is from Germany and WWII (Tome VI) : "The supply situation of 6th army-as indeed that of the other armies in the area of AGB-was therefore exceedingly tight during the weeks prior to the opening of the Soviet offensive,in many respects it was quite catastrophic ."
The whole problem of the air supply of Stalingrad is since 70 years discussed very partially (for obvious reasons) , the air supply of Stalingrad can not be discussed apart from the supply of the 170000 men who were not encircled .
What should have priority is the available supplies;than one could look at the difficult question of how much was needed(the estimations are diverging from 300 too 750 tons daily),one should also not forget to double this figure: if Stalingrad needed daily 750 tons, so did the other part of 6th army that was not encircled ,and finally one could look at the number of supplies that arrived at the cauldron .
And there is also the tricky question if after Uranus, the forces outside Stalingrad did not have priority at the expense of those in Stalingrad .