Part 107 UAS Pilot reported an NMAC with a low-flying plane during flight. The UAS pilot commanded evasive action of the UAS to avoid collision.

Narrative

EventsOn Day 0; I was flying a commercial real estate photography mission in Location A in Class G airspace.At XA17LT; while the sUAS was at 400 feet; and approximately 400 feet laterally from me; I heard the sound of an airplane. Upon recognition of such; I promptly began to descend the sUAS in order to give right of way to the airplane. I could not visually see the airplane; but I could tell by the increase in volume of the sound that it was coming in my general direction. I had the sense that something wasn't right; and so I instinctively stopped the descent of the sUAS at approximately 250 feet AGL. I looked toward the sound; and almost immediately; I saw a GA airplane pass directly overhead; from north to south; across the road; at approximately 125-150 feet AGL. This means that the lateral separation of the two aircraft was approximately 400 feet; and the airplane was more than 100 feet below the sUAS. The airplane was also several hundred feet below its floor of 500 feet in non-congested areas.Based on the low altitude of the airplane; and my perception that it was at a high throttle; it led me to think that something wasn't right and to wonder if the pilot was in distress. I had an airband radio in my car; which I tuned to 121.5 in order to listen for any activation of an ELT. I did not hear any ELT.I pulled out my sectional chart and looked to see if maybe the plane was on final to an airport to the south. There was no airport in that direction; however; I did notice a small grass strip runway (ZZZ) approximately one mile to the east. LessonsThe cause of this event was the airplane flying below its minimum altitude. In future flights; I will expect that other aircraft will be in places where they shouldn't; and I should be on the lookout for the unexpected.During future flights; I will make sure to make sure to have my airband receiver tuned to the local tower or CTAF frequency to increase my awareness of airplane activity in the area.The particular sUAS I was flying does not have ADSB-in. I will investigate add-on solutions to have awareness of ADSB beacons from airplanes when flying this sUAS. I will investigate add-on solutions to have awareness of nearby airplane altitudes when flying any sUAS.When flying in the general vicinity of an aerodrome in uncontrolled airspace (in this case; a private grass strip); I will attempt to make contact with the manager or operator ahead of time in order to let them know I will be performing sUAS operations in the area and ask if they have any flights planned that I should be aware of.