In general, a jet is much more likely to be coordinating with ATC even if they aren’t required to under the specific circumstances. But still, this was a failur

In general, a jet is much more likely to be coordinating with ATC even if they aren’t required to under the specific circumstances. But still, this was a failure of ATC to provide adequate separation from an aircraft that they knew was operating under Visual Flight Rules, and was not under ATC control. The Cessna pilot is under no obligation to maintain contact with ATC in this airspace, and it is the job of ATC to route the aircraft under its guidance around this kind of airspace, and if penetration of uncontrolled airspace is required, then to advise about and route around any known traffic. The Cessna was probably communicating with the relevant CTAF or tower frequency for the airport it was setting up an approach for, or monitoring Unicom for traffic avoidance for other small VFR aircraft. A single pilot can’t fly, navigate, and maintain traffic separation in a plane and communicate on all frequencies at once simultaneously, and ATC does not have the resources to control all random manoeuvres of small aircraft. This is why there are places where small aircraft operate, mostly under “see and avoid” VFR rules, and places where all operations are done under strict ATC controls. In this case, the heavy aircraft was directed to fly through one of these uncontrolled areas, and the controller failed to maintain adequate separation from uncontrolled operations.