What drove be to bankruptcy was over leveraging, full stop. I made a dramatic mistake in game play. That was not the point I was (poorly) trying to make.
Perhaps if I were at a larger base, it would not have been a problem, as I would have more of each aircraft type to work with (I had around 10), but the only room for me to expand would have entailed my going smaller into the (not very profitable) 35-40 px routes, which would have been the magic 4th type (going into the unproftibale sector as well). If I were in a market that would have use for very large aircraft, I would be in the same position, unable to expand without going into the 4th aircraft type.
Were I playing with an aircraft with families, I could have done what I did with 2 types pretty easily, giving me a third to expand into.