here are the bits as I've come to understand them:

- there was a similar incident just the day before where a helicopter's path came close to a similar plane. It was high enough, so the plane received the TCAS (traffic alert/collision avoidance) 'resolution advisory' warning and made the proper actions.

- warnings from TCAS are inhibited under 1000ft because they would be full of false/nuisance warnings that close to the ground and potentially suggest unsafe evasive maneuvers.

- the helicopter was following a designated route along the river as the general guide

- the helicopter went a bit higher than the designated ceiling (and that probably happens pretty often).

- the incoming airplane was following the 'glideslope' of the 'instrument landing system'

- the helicopter crew may have been wearing night vision goggles. such goggles can affect ability to see periphery. Also, nighttime lights of a city can appear bright and distracting.

- the helicopter crew of 3 may have been less than other similar flights

- airplane was initially looking to land on the longer runway #1 but was asked by the ATC to use #33 instead (their smaller plane could use it fine). They
take awhile considering it and then accept it. They had to slightly change the angle of their approach. This may have been a choice to simplify the workload for the ATC controller.

- There was one controller handling both the plane and helicopter traffic and one left earlier

- the plane and atc use VHF to communicate while the military helicopter uses UHF, thus, the plane had no awareness of any communications with the helicopter

- the ATC mentions the presence of the plane to the helicopter. the helicopter says they see them and request "visual separation" which is basically 'we can see them, so we can move around them accordingly'

So, it's possible the helicopter was looking at a different plane/set of lights when they mentioned that they had them in sight. Another plane had just taken off from runway 1. It's also possible that they saw the CRJ plane and just misjudged its location (maybe due to the turn they were making for the alignment to land?).

As for systems issues, it seems there's no way for ATC to know just which plane a helicopter (or other plane) is referring to when they 'confirm' seeing it.

It's interesting to note that some airlines actually forbid "visual separation" at nighttime due to the safety concerns (misidentifications, conflicting city lights, human perception). (eg, KLM (https://www.youtube.com/watch?v=7rdapQfJDAM)) US ATC might prefer visual separation which means that planes can be closer together in lining up to land whereas an instrument approach means a bigger gap. (More planes landing means more money for airports?)

It seems like the 'glidescope' area when landing should be treated like a 3d extension of the runway -- keep planes and craft out of it during a plane's landing. Anything crossing into it should be treated like a "runway incursion" (which is also clearly a problem that the US needs to fix...In someways, this crash might be seen as an extension of that issue?)

There needs to be a way to verify just which planes a craft is "confirming visual' of - especially at night.