"Non combat" losses in the VVS included aircraft which were simply worn out or considered too old and scrapped, and this explains for a large part why the figures of non combat soviet losses are so high...
Here is an example,
however incomplete of the way the losses were counted :
http://my.tele2.ee/airacesww2/airace...losses1944.htm
By the way, to judge correctly the level of Il-2 losses, it would be necessary to compare them with the number of sorties achieved : e.g. : AFAIK, the loss per sortie rate was (very) much higher in 1942 than in 1944 while overall losses were lower...
Hope this can help,
Kolya.