If anyone has read Roald Dahls book going Solo, he was actually in the same Squadron in Greece as Pat Pattle, a bit of a forgotten campaign, the BEF was really outnumbered and outclassed in that one, quite an interesting campaign as well.
On the P-39, there are some other points to consider, most covered in the articles below.
There is a very interesting, often amusing (but rather long!) interview with a soviet pilot who flew many types here, which probably explains most of it, I'll add some quotes below.
http://lend-lease.airforce.ru/english/articles/golodnikov/part1.htm
and some more articles on Soviet aviation lend lease aircraft here
http://lend-lease.airforce.ru/english/articles/index.htm
and from other articles
On the P-39, there are some other points to consider, most covered in the articles below.
There is a very interesting, often amusing (but rather long!) interview with a soviet pilot who flew many types here, which probably explains most of it, I'll add some quotes below.
http://lend-lease.airforce.ru/english/articles/golodnikov/part1.htm
and some more articles on Soviet aviation lend lease aircraft here
http://lend-lease.airforce.ru/english/articles/index.htm
Returning to the Airacobra, it must be noted that the British somewhat underrated it. Soviet pilots preferred the Cobra despite its many shortcomings to any other aircraft received from the Allies, including the Spitifire VB, which the British deigned to give us only in 1943.
While completing the account of the Airacobra I in Soviet aviation, the following conclusions can be drawn. Despite a number of design deficiencies of this first model of the air frame (undercarriage weakness, engine seizures, inadequate rate of climb, tendency to flat spin), it was a threatening weapon in the hands of skilled aerial warriors. As was written in the summary of the commander of 153d (28th Guards) IAP regarding the combat work in the Voronezh and West Fronts in July-August 1942, "The Airacobra aircraft is considered by the Germans to be the most dangerous enemy and should be engaged in combat only when they [the Germans] have numerical superiority and the advantage in altitude and surprise." Therefore, the decision by the VVS command regarding preliminary serious study of the aircraft and its testing and subsequent delivery to units that had combat experience turned out to be correct. Combat tested and experienced pilots were able to master the correct tactical employment of the airplane in a minimal period of time. They learned to compensate inadequate vertical maneuver with good formation flying, echeloned by altitude (pair above pair with 100-200 meter interval). Mutual fire support also made possible minimal losses and maximum damage to the enemy. The most clear example of this was in the 19th Guards IAP, where group kills were almost three times greater than individual kills. A year later A. I. Pokryshkin, the creator of the celebrated "Kuban' bookshelf", arrived at this same "group" tactic independently and in more complete form. The conclusion regarding whom the Airacobra engaged-slow-moving transports and aging bombers, or Messerschmitts and Focke-Wulfs of the latest models, can be drawn from the statistics presented above.
and from other articles
Russians doggedly supported their Army with massive air support.
Flying the lower altitudes gave the higher flying German aircraft a distinct advantage
and used well tested Boom and Zoom to pummel the lower flying planes.
Yet the vast majority of German Aircraft were shot down a lower altitudes.
The Russians played a bait game to attract the Germans to attack and
used B&Z tactics to force them into energy waisting turns compromising excape.
The P39 could climb with the German 109 with the deletion of the 4-30 cal up to 18K.
Regardless of the tactics the Russians lost 2 to 1 over the whole course of the war.
But Russia could sustain the losses better with new manufactured aircraft
and their factories were never attacked by the Germans to slow production.
This was a war of attrition. Who had more war materiale and men(women) was going to win.
Especially with the Allies on the Western fronts eating away at German resources.
The attrition developed excellent Russian pilots.