Well, the chance of hitting an airplane with a drone at cruise speed is very slim to begin with - cruise speed usually also means cruise altitude, and drones don't usually fly several kilometers high.
But the main risk is getting something into the engine that is hard enough to break off a fan blade. These blades are made from an extremely hard, somewhat brittle alloy, and spit at very close tolerances to the outside of the engine to achieve high efficiency.
If one breaks it gets ingested, and it's made from the same hard material as the other blades are so it can damage them easily, breaking more of the engine up as it goes through resulting in catastrophic cascade failure of an engine.
Now i'm not sure what the hardest part of a drone is made from, but i could imagine things like titatnium being used for the frame of higher end models.
And odd as it may seem, a jet engine can survive ingesting something as big as a goose (say 4 kilograms of poultry) without much damage, but if you throw a one ounce titanium bolt into it, it'll be destroyed.
I won't be something like the plastic body or even rotors on a drone that do the damage, it's the harder metallic parts, even if they are not that big (like the motors).
Are there titanium drones for sale to the public? There are metals in the motor, but I would think mostly copper, aluminum and some very tiny magnets made of ferrous rare earth alloys. I'm sure the reason that drones aren't allowed near airports is because we don't want to find out the hard way if they will damage an engine. I just don't know if there is anything hard and big enough to do that on drones sold to the public. I also doubt anyone has done the necessary testing to unequivocally answer that question.
The thing is, you need to get PRETTY close to the engines for the drone to get sucked in. At that point, it's not even worth it because your camera would be too zoomed in to even see. Also, some cameras are quite inaccurate when it comes to showing distance; so sometimes we won't even know how far the drone is, it could be a couple of hundreds of metres away for example.
Oh well, hopefully, no idiots try to attempt to fly a drone into an engine!
Well, in aviation aircraft coming closer to eachother than 500 feet during flight are considered to be near misses (or technically near-mid-air-collissions or nmacs). I can't really tell how close that drone came to t hat plane due to the unkown zoom angle of the camera, but it's too close for comfort.
As far as the risks of drone ingestion by a jet engine it's a bit vague: Bird ingestion has been tested extensively by just throwing bird carcasses into running jets secured to the ground.
The problem is that birds are of fairly uniform consistency: a turkey surely is larger than an chicken, but they are basically made out of the same materials.
With drones this may be a bit of a different story: surely you could test what happens to a jet engine when you shove a DJI phantom through it, but there are so many different types of drones and possible camera's mountable on them it would be very difficult to test for all scenarios.
Especially with the larger drones this is a problem as people can mount all kinds of camera's to those, anything from a simple compact to a big dslr with any lens.
Even if the drone as such gobbles up a DJI phantom just fine that doesn't really guarantee it will be okay if someone mounted a 600 mm tele lens to another type of drone and that got ingested. And given such lenses often contain hard glass elements damage could be extensive even if the drone itself got chopped up just fine.
I'm surprise with all the media Hype of drones
being the new Evil Menace that will bring down
an Aircraft full of passengers.... that no one
has actually done any real life tests destructive
tests like they did with birds.:undecided:
They do quite extensive tests on jet engines for bird ingestion, which basically involves just throwing birds of various in a stationary mounted jet engine running at various power levels.
Similar tests are done on ingestion of water and such, and it is amazing how much water you can run through a modern jet engine before it flames out.
Perhaps they are already doing tests on drone ingestion as well, but not reporting the results publicly just yet.
There is also the question of if and how drones could be used as a deliberate method of attacking an aircraft, rather than an accidental ingestion or collision with a single drone operated by someone stupid enough to operate it closely to aircraft.
I doubt an average drone like a DJI Phantom would actually cause a flight to crash, it could disable one engine worst case, and that'd be a hairy flight back when taking off, and only a small safety problem when landing.
But what if it was done deliberately by terrorists? I doubt a plane would survive a situation where you shove, say, 100 drones down each engine just after take off at the end of the runway: nowhere to land, no altitude to glide back, so it'd be on the ground not very far beyond the runway.