Was out with my MA2 filming the sunset last evening on a beach in Oregon. I was up about 200' in altitude, when out of nowwhere a single engine high wing plane and an ultralight buzzed the beach. They came up from behind a large dune, and I had almost no warning--and I did not get any DJI Airsense warning even though I have it turned on. The only thing I could think to do was drop down immediately to about 20'. They flew by so fast it was hard to say for sure what their altitude was, but I'm guessing no more that 200-300'. Any idea why Airsense wouldn't kick in--at least for the plane? I can see how an ultralight might now have that technology, but was surprised the plane didn't. I did check--it was not a restricted zone......