liz says:

Best take I’ve read (at least the best from an “outside” before we have more information from the accident investigation, assuming it is released to the public:
https://x.com/Mark_McEathron/status/1884849637066260815

‘”I was a Blackhawk helicopter crew chief in the Army.
I was even a Flight Instructor. This means that I trained Crew Chiefs and ensured that they completed all training annually to maintain their flight ratings.
One massive responsibility we had was to be the eyes for the pilots. We handled airspace obstacle avoidance and communicated potential risks to the pilots.

Quite often we would train as a flight of 2 or 3 birds flying in formation.
It was my job to have my head out the window and tell the pilots that the aircraft behind us was “staggered right at 3 discs”. (We measured close distances in terms of the diameter of our rotor discs).
I can tell you after doing this for hundreds of hours, even when you know EXACTLY where a Blackhawk is, and you have night vision goggles on, it is EXTREMELY hard to SEE the aircraft.
These birds are designed to be hard to see at night.
The red and green lights on the side get lost in the lights of the city below. The only “lights” on top of the aircraft are called “slime lights” because they are a very very very dim green.
Incredibly difficult to see.
If you are above the helicopter, even if it has it flood light or spot light (2 different lights) on, underneath it, it is still hard to see the bird because all of that illumination is below the airframe.

Another thing people should know is just how busy things can get on the aircraft.
Pilots are talking to each other about what they are observing on the instrument panels. This means neither are looking outside the aircraft.
The crew chief might be conducting a fuel check, where we would also be looking up into the cockpit at the fuel gages and the clock.
This CAN lead to moments where all 3 people on the aircraft are all looking inside the aircraft.
It’s not supposed to happen that way. We are supposed to announce when we are “coming inside” or are “back outside” the aircraft. But that doesn’t always happen.
Also, in cities like DC, the radio traffic is constant and can make it hard to filter out what is important for you to listen to.
Checking instruments, doing math, reading checklists, and listening to multiple radios all at the same time is HARD. Mistakes happen.
Anyone out there telling you that they find the aircraft collision to be suspect, have NEVER been in a flight crew and they have ZERO idea what they are talking about.
Ignore them all. Better yet, mock the hell out of them.
999 times out of 1000 aircraft incidents always come down to a series of pilot and crew errors.
Humans are involved. They aren’t perfect.
Tonight, my heart and mind is with the families of those involved in this tragic event.
I won’t join the chorus of idiots making speculations.”

GWB says:

Based on what little information I have (which includes the audio, with the acknowledgement of visual clearance, and the video from across the river), and my knowledge of flying, here is my brief guess at what happened:
Blackhawk is flying across the arrival flight path of Reagan, for some unknown reason. It’s a bad idea, IMO, but it’s a busy area. (Procedural protection would have you just staying out of the friggin’ flight path, altogether.)
ATC sees the two aircraft in close proximity (not defined the same as you might just looking at aircraft in the sky; it’s a lot further than you might think) and calls it out to the helicopter.
Note, however, ATC calls it out as a CRJ. Which is fine during daylight hours, but this is in the dark. Even with NVGs on I doubt most could discern a CRJ from any other type of aircraft except maybe a Jumbo jet. I’m not saying ATC did wrong with that, but it might have been information that just overloaded the pilot and caused other information to not settle into the pilot’s mind.
Watching the video, there is a departing aircraft you can see. Or, perhaps it is maneuvering to line up behind the Wichita flight. But it is there, with its landing light on.
Who knows if the pilot said “Yes, we can see it” and was talking about the same aircraft? He’s now fixated on the wrong airplane, watching it as he crosses the path of the other aircraft.
Watching the video (and, admittedly, it’s a long way away), there are no sudden maneuvers by either aircraft. This just isn’t possible, even with the lesser ability to see closure at night. You can see the lights on the aircraft, and at some point they get obviously much too far apart (with a big blank spot in-between) to not be a problem. So, I surmise the pilot was looking elsewhere.

And all of this is split over at least 2 brains. There are 2 crew flying the aircraft, and they split the responsibilities. The co-pilot (assuming) is on the radio and hears the call-out. He says to the pilot “Do you have it?” and the pilot says “Yeah, I got it.” With great cockpit resource management the co-pilot says (or the pilot assumes and does it without prompting) “Point it out to me” and the pilot does. And if the co-pilot now thinks “I don’t think that’s what was called out” he says so and they begin to work to make sure they get it right. But it’s likely that part didn’t happen. So the co-pilot thinks the pilot is handling it, and replies back to ATC that they’ve got it covered. A minor lack of coordination between the two halves of the brain.

I note also that it appears ATC stops watching after the helicopter says they’ve got visual separation. There’s no call-out of merging tracks. So, no last-minute save from the guys who could see the aircraft with “God’s-eye view” on radar. We also do not have the ATC radio traffic to/from the American flight. That is evidently a different controller – another separation of halves of a brain. (And, as with the helicopter, it’s a necessary division of tasks/brain power.)

That’s an analysis with what limited info I do have. And it’s a tragedy. As liz points out, mistakes happen. But these are mistakes that, unfortunately, kill lots of people. I see 3 possible issues in the chain of events, and we might find more as the investigation ensues. Pray for all of those who lost someone in the crash.

“Flying isn’t inherently dangerous. But it is terribly unforgiving of even small mistakes.”
/a flying pioneer whose name I don’t remember