I don't see that at all. Any recent evidence?
UKAB Reports
There are many instances of aircraft getting close enough to “cause concern” to the pilots or ATC. Often, they have some form of electronic conspicuity and/or are talking/listening on the radio but although there is enough data in retrospect to prevent the near-miss, it wasn’t available to assist at the time, e.g. a controller can see two dots converging on his screen (and maybe gets a STCA) but the aircraft aren’t on his frequency; one has FLARM, one has a XPDR; one is on an en-route frequency, the other on SafetyCom and so on.
That’s one of the frustrations: there is a lot of “here I am!” going on but because of the diversity of position reporting and receiving equipment on smaller aircraft, there are many cases of the data to prevent a near miss or collision being available but not collated/interpreted in real-enough time to help...
The Kitfox/Cessna 177 accident is the last one I can think of. En-route midairs cause a very small proportion of aviation fatalities. I share the concern re. the risks to GA if someone were to bring down an airliner but mid-air collisions with other small aircraft are fairly low on my list of concerns - well below the weather, carb-icing and all of that.
There were c.50 Airprox reports in 2016 that were graded at the highest risk category, “A”, in that the separation was small enough it was purely down to luck that the aircraft didn’t collide. Remember this is just from pilot & ATC reports - those that “pass in the night” are not recorded.
There were multiple fatal midairs in 2016, I haven’t researched the exact number but it was significant.