Don't quote me on this but I heard from some place years ago that unless you 
are on an ocean, you are just mobile and not maritime mobile compared to 
being on a lake or river for example.  The same is true, I believe, with 
aeronautical mobile.  That means you are flying over an ocean.  Otherwise, 
flying over land, you are just air mobile or mobile period.  I don't know 
this for certain but I think the great lakes are calculated in miles instead 
of nauts because they technically are not oceans.  I'd be curious if any of 
this old memory is true or not.  I know rivers are measured and calculated 
in miles instead of nauts but as soon as they empty into the oceans, it 
changes to nauts instead of miles.

Phil.
K0NX