In FS2000, I could manage some risky behavior that no sensible person would attempt in real life--landing on bridges for example, between the suspension cables and superstructure. I could put a Cessna down on the Golden Gate.In FS2004, my attempts to land on bridges trigger a "building crash" even when there are several feet of clearance around my aircraft. I'm sure there is no way to tweak this, but it's just an observation.

just turn off crash detection in the realism settings.--

One thing you might can fix / adjust is the model radius of your aircraft - make it smaller. AITM, AFCAD and ACPM all have aircraft editors which can make that change. Though mainly intended for AI - it works with almost aii aircraft - though I would not try it without making a backup of the model file and would not try it with a payware user aircraft.The visual model means nothing to FS as far as crashes - it's all the size set in the models - your aircraft and the object.