It happened a week ago, but this 757 PHX-OGG (Kahalui, Maui) was about midway between LAX and Hawaii when there was smoke in the cockpit/cabin. It is probably the worst nightmare, the possibility of an in-flight fire over 1100 miles from the nearest runway. The plane diverted to the nearest airport (SFO) which was about 1160 miles away.
The navigation issues sure are different nowadays than they were a few decades ago!
Featured Maps: US Airways Flight 432 Diversion (19 September 2010) - Great Circle Mapper
FlightAware > US Airways #432 > 17-Sep-2010 > KPHX-PHOG
Incident: US Airways B752 over Pacific on Sep 17th 2010, smoke in cockpit