Can "a drone" damage the wing of "an aeroplane" to the extent it actually threatens its ability to fly? I stumbled across this video by the University of Dayton, showcasing the amount of damage a certain type of drone can do to a wing, and they wrote a whole article about it. While most of said article sounds like marketing for their research institute with very little actual information about the video they just released, the key thing to take away seems to be that:

researchers in UDRI’s Impact Physics group launched a 2.1-pound DJI Phantom 2 quadcopter at the wing of a Mooney M20 aircraft. The drone did not shatter on impact, but tore open the leading edge of the wing as it bore into the structure, damaging its main spar.
[...]
The researchers then fired a similarly weighted gel “bird” into a different part of the wing to compare results. “The bird did more apparent damage to the leading edge of the wing, but the Phantom penetrated deeper into the wing and damaged the main spar, which the bird did not do.”

If we trust that the researchers accounted for the fact that a damaged wing's structure is obviously compromised in places and that they also accounted for bones making an actual bird slightly more rigid than pure gel, as well as repeating the experiments often enough to make above statement with a reasonable degree of confidence -- none of which the article mentions explicitly -- then what conclusions can we draw from this?
It looks dramatic. Sounds dramatic, too, if you know nothing about aviation at all, which I guess was the intention when they wrote the article.
But how significant is the damage really?
The article doesn't say.
One YouTube comment by one &quot;Stephen Mann&quot;, appearing to claim piloting experience states:

You can throw, at 200 MPH, anything weighing 2 pounds at a sheet of 2024-O .04&quot; aluminum, typical of aircraft wings, and get this damage.  I've seen worse hail damage.

and notes that:

the Mooney wing uses a thinner aluminum (0.038&quot;) than an airliner (0.04 to 0.05&quot;).  This made the Mooney lighter and faster, which was a marketing design.
I've had more than a few bird strikes during landing (none during takeoff that I was aware of).  Some were Canadian geese that weigh 10-15 pounds.  There was never any damage to the aircraft beyond cleaning up the bird guts from the wing.

while generally playing down the significance of the test:

Typically, no aircraft below 400 ft., where most drones operate, will be flying that fast.  On final approach most airliners are flying between 130 to 160 knots, and by the time a landing aircraft is below 500 ft. the flaps and slats are deployed and the A/C is probably going 120 knots.  General aviation aircraft, like the Mooney in this video, are typically flying between 70-110 knots on final approach.  Even slower on takeoff.

I'm reluctant to accept information from YouTube comments at face value -- especially since it may be biased. But if true, this may just reduce the usefulness of the test significantly. And although I guess that's quite possible, I'd like to think they put some thoughts into these experiments before conducting them.
So where does that leave us?
Can &quot;a drone&quot; bring down &quot;a plane&quot; by crashing into it? Most likely, if we're talking about these big US military type drones like the RQ-4.
But can a &quot;hobby drone&quot; (for lack of a better word) like the one shown in the video by the University of Dayton seriously threaten the fly-ability of &quot;the average plane&quot; (if such a thing exists)?
Or let's say we start at the Mooney and scale the damage up for larger planes. Would a plane with that kind of damage get into trouble whatsoever or would it just require a probably costly repair?
Mr Mann doesn't have a clue what he's talking about.

Wings aren't made from 2024-O aluminum, which is fully annealed and very soft.  The usual heat treat state is T3 through T6.

A Mooney would NOT have .040" wing skins.  The skins will be .016, .020, .025 and maybe .032 in high stress areas around the wing roots. Leading edges would be .025 or maybe .032 inboard, and likely .020 or .016 near the tips and on the control surfaces.  Skin sizes are for structural efficiency and rigidity for minimum weight, not "marketing"... geez.

His approach speed comments are more or less correct, but a Canada Goose will do significant damage to any aircraft it hits in flight and has a good chance of bringing down a Mooney at any contact point.  A Mooney running into a goose at the wing will, at minimum, completely crunch the leading edge in back to the main spar.  A goose will do significant damage to the slat or leading edge of any airliner.  There was a CRJ900 that hit a goose size bird just below the windshield on the takeoff roll near V1, and it came back into the pilot's instrument panel, distributing guts and feathers all over the place.

Geese are bad news and are a vexing problem in the spring in central North America.  The terrain is all browns and if you are descending with a flock below and in front they are nearly invisible until you are passing through their level.

A goose hitting the windshield in front of the pilot or horizontal tail of a Mooney or similar light aircraft will probably bring it down.  On the wing, maybe.

A 2lb drone will do obvious damage as the test showed but would not bring down a Mooney unless it hit the windshield, incapacitating the pilot.  It would certainly go though a windshield.  1/8" plexiglass has roughly the same tensile strength as .020" 2024T3.   You wouldn't want to hit anything heavier than a few ounces with 1/8" of acrylic in front of your face as the only barrier.

So from that standpoint, drones of any size can be considered a hazard to aircraft.