We do a lot of megger testing on commercial aircraft these days. Its not good enough to just check for continuity and shorts to ground with a regular DMM. We megger most of the wiring. It checks for insulation breakdown and problems to come.

The megger uses high voltage (either 500 or 1000 vdc) to test the wiring to its neighbor, or to ground. For me, anything over a few meg ohms is open. Some tasks specify a certain reading. Like over 150 meg ohms.