I've noticed this yesterday in a flight just before landing and I found it funny how the airplane was following the roads each for a few seconds before snapping of.

I also confirm it snaps on both google maps and apple maps with airplane mode turned on, most probably due to caching.

I've also found it amazing that the iPhone 6S held the cache of a map 3000km away after 3 days abroad, with intermittent wifi and lots of google maps and safari use.