Bombers

Way late reply, but I think they were Mitsubishi G4M "Betty" bombers...

Or they were supposed to be.

..Joe

Can't remember in which scenes but there were two bomber types shown. The single tail model was probably the Mitsubishi G4M 'Betty' as was already answered and the twin tail model was probably the Mitsubishi G3M 'Neil' bomber. I'd like to add though that since this movie takes place before 1941, the year the Betty bomber first flew, the aircraft was probably supposed to be something else like the Mitsubishi Ki-21 'Sally' which looks a lot like the Betty.
KS