thanks wiggy. that makes a lot of sense for weather diversions, and for that reason aircraft are to climb/descend 300 feet depending on track, and thus avoiding other aircraft doing the same. After all, if weather affects one aircraft, it's likely to affect others.
An engine failure seems to be a totally different animal. Not a short term diversion, but perhaps an hour or two of flying where posssibly another aircraft is within 15 miles (plus or minus) plus 500 feet altitude difference. I'm just surprised it isn't 30 miles for an engine failure, that's all.
30 miles seemed to work before....