[GuerraCivil]

While waiting for the Osprey book on ROCAF aces, I just make a rough guess that at least half of IJNAF aircraft and personnal losses were caused by enemy activity (= in combat). If 554 IJNAF planes were destroyed by all causes during operations of China 1937 - 1941, then about 270 - 280 aircraft may have been direct combat losses (air combat, enemy AA) and of the aircrew casualties of 680 the combat losses perhaps more than 50 %.

I just make this guess on comparison with Soviet aircraft losses during Winter War which in total may have been as high as 980 (in the period of three and half months of 30.11.1939 - 13.3.1940). It has been estimated that approximately half were combat losses. But at least half were caused by accidents: engine and mechanical failures, bad winter weather causing orientering mistakes and insufficient training of some pilots.

To my knowledge Japanese pilots were well-trained and their planes had good stability and were relatively easy for an average level pilot to handle. For example A5M and Ki-27 fighters were less demanding and more forgiving for a average pilot than the Soviet I-16. Relatively easy-to-fly planes with good pilot training may have diminished also the number of accidents. But of course the period 1937 - 1940 is rather long, and airfield conditions in China were not always ideal.

I´m not aware of the "average accident rate" of IJNAF/IJAAF, but I guess it was less than that of Soviet air forces during Winter War. And thus accidents and other "not-enemy related" caused perhaps less than 50 % of total losses.

But this is of course speculation as long as more detailed info is available.

And although IJNAF seems to have been the more important air force in China in 1937 - 1940, the IJAAF took also part scoring both air victories and suffering some losses. I do not know much about IJAAF´s combat losses in China because the available info in internet is quite fragmented, focuses mostly in few combats and tells actually little. For example the info presented in Håkans Aviation Page has these faults - it has lots of details taken from various sources, but...

...it is not the whole picture and there is no easy-to-read summary of Chinese-Japanese airwar with clear numbers of combat losses and confirmed air victories of both combatants during different years.