Darrell Feller, a retired U.S. Army National Guard pilot, is weighing in on the possible causes behind the tragic D.C. aircraft collision … sharing how a number of factors could’ve been at play.

We caught up with Darrell on “TMZ Live” in the aftermath of Wednesday night’s tragedy, and he explained how it was entirely possible the Army Black Hawk helicopter, which crashed into a regional jet carrying 64 people, didn’t even see the aircraft coming.

Darrell says the particular route the chopper took is known for causing “confusion with ground light,” due to the light from surrounding structures, buildings and other aircraft.

Darrell said this particular route, combined with the assigned runway, is known as the “most dangerous spot” … which means an incident is most likely to occur there — as it did this week.

While the route has been shut down by the FAA following the collision, Darrell made a case for its existence … explaining it allows Air Traffic Control a clear way to move aircraft in and out of congested airspace.

Darrell said something will have to be done about the danger zone … but shared it’s unclear if that means closing the tricky runway, or creating a new routing system entirely.

There’s currently a federal investigation into the cause of the collision … which left no survivors.