In article , "Mike & Janet Larke"
writes:

I'd also be interested of there's any difference between this on the
southern border, and, say a Detroit - Rochester NY flight overflying
Canadian airspace en route.

Flying over Canada with takeoff and landing in US requires only that you file
(and activate) a flight plan - either VFR or IFR.

There is a ADIZ along the southern border, so crossing back into the US has a
few more hoops to jump thru. Call ahead, have 12 inch numbers on plane, smile
when the F16s go by, etc.

Chuck