The following story of fateful forgetfulness occurred between Führer and Chancellor of the German Reich Adolf Hitler, Luftwaffe Commander-in-chief Hermann Göring and Luftwaffe Chief of Staff, Colonel General Hans Jeschonnek.

On 28 June 1942, Germans launched Fall Blau, a major-scale offensive initially aimed at capturing the Soviet oilfields at the Caucasus. On 23 July, Hitler split Army Group South in two, ordering Group A (Generalfeldmarschall Wilhelm List) to continue drive south for the Caucasus - and the Group B (Generaloberst Maximilian von Weichs) to cross the Don and drive east towards Stalingrad. On 23 August, German XIV Panzer Corps has reached the northern suburbs of Stalingrad; on 27 September, Soviet resistance in the city has been limited to two narrow, split sectors on the banks of Volga.

However: on 19 November, the Soviets unleashed Operation Uranus, aiming to crush the stretched and exposed Axis flanks and encircle German 6th Army. As the Soviet encirclement operation was completed on 23 November, some 300,000 Axis soldiers were locked in a pocket approximately 775 square miles (2000 square kilometres) big – with no reinforcements and no ground supply lines.

On 20 November, Hitler summoned Jeschonnek to his Berghof residence in Obersaltzberg. The matter of the discussion were prospects of maintaining a temporary air supply bridge while the ground relief effort is organized by Generalfeldmarschall Erich von Manstein and his newly former Army Group Don. Under these specific circumstances, The Chief of Staff has assured Führer that a temporary air bridge is feasible – as long as both transport planes and bombers of Luftwaffe's VIII Air Corps are used for the sole purpose of carrying the supplies.

On 22 November, Hermann Göring arrived at Berghof. Despite persistent objections from Army's Chief of Staff General Kurt Zeitzler, Luftflotte 4 Commander Generaloberst Wolfram Freiherr von Richthofen and VIII Air Corps Commander General Martin Fiebig, Göring has committed to the plan of supporting the Stalingrad pocket by air.

Meanwhile, the 6th Army staff scaled down it's 750 tons-per-day demand to 500 tons – quota considered by them sufficient for the Army to remain operational. Göring scaled that number down further, to a bare minimum amount of 300 tons per day – disregarding the fact that the 6th Army has originally put forward inflated numbers to cover for the days which would be unsuitable for flying due to the winter weather.

On 23 November, Hitler was on the phone with Jeschonnek. At this point, having received the previous reassurances, he wanted to know whether the Luftwaffe has the means of delivering 300 tons of supply per day to Stalingrad. Prior to answering, the Chief of Staff has narrowed the question down to: can Luftwaffe deliver 300 Versorgungsbombe (Supply Bombs) a day to Stalingrad, given that each Junkers Ju 88 and Heinkel He 111 could carry three of those? Accounting for the available resources at the time, the answer was: yes.

Jeschonnek forgot one crucial detail: Versorgungsbombe, despite it's name, differed from a typical, general-purpose SC1000 bomb as it could only hold 750 kg (and not 1000 kg) payload. Therefore, the Colonel General's whole calculation was flawed, meaning that reaching a 300 ton quota required either more planes than were available or additional sorties beyond the Luftwaffe's reasonable capacity. The same day, having reexamined the math, Jeschonnek informed Hermann Göring about his error; Göring, having already reassured Hitler about the air relief himself and having repelled Zeitzler's fierce objections in front of the Führer, ordered his subordinate to leave the matters as they were.

On 24 November, Hitler has informed General Friedrich Paulus that his 6th Army is to organize hedgehog defense and not to attempt a breakthrough, as the encirclement will receive air support until another ground offensive operation relieves them.

During the next 71 days, winter weather, accidents, Soviet anti-air warfare combined with shifting strategical situation that increased flight distances while decreasing the number of suitable airfields and operational planes have allowed Luftwaffe to meet the 300 tons supply quota only three times. There were 8 documented flightless days with no supply delivery altogether and 7 days with supply deliveries not exceeding 20 tons. The average daily delivery through the existence of the air bridge has turned out to be mere 117.6 tons a day.

On 26 November, German 6th Army reduced it's food rations for the first time; on 8 December for the second time; on 25 December – for the third time. By the end of the siege, the food ration has been cut to one-sixth of a normal ration.

On 23 December 1942, German's 4th Panzer Army offensive to relieve the encirclement has collapsed some 30 miles (48 kilometres) away from Stalingrad. On 16 January, the Red Army overran one of the two key supply locations inside of the pocket - the Pitomnik airfield. On 21 January, the Soviets overran Gumrak, reducing Luftwaffe air support exclusively to drops. On 31 January, General Colonel Friedrich Paulus received a promotion to Field Marshall – and surrendered to the 64th Army of General Vasily Chuikov. On 2 February 1943, the last organized forms of Wehrmacht resistance in Stalingrad have surrendered.

On 18 August 1943, Colonel General Hans Jeschonnek has committed suicide by a gunshot. His death note mentioned the inability to work with Göring any more.

Sources:

Joel S. A. Hayward - Stopped at Stalingrad: The Luftwaffe and Hitler's Defeat in the East, 1942-1943 (1998)
Janusz Piekałkiewicz - Stalingrad: Anatomy of a Battle (1995)