Tons of people are searching for a reason behind the plane crash in Washington, D.C. that has claimed dozens of lives ... and, new video shows just how close helicopters fly to commercial planes.

A user on X posted a clip late Wednesday night ... sharing a video he says he took six days ago -- showing two helicopters flying to the left of an airplane as it takes off from a runway at Ronald Reagan Washington National Airport.

Check out the vid ... there's not a huge gap of space between the choppers and the plane -- though they do seem to be a safe distance away.

Worth noting ... the video's taken during the day -- but, the fatal D.C. crash happened at night, so this is much clearer visibility than pilots of the crafts would've had.

The social media poster openly questions whether this short distance may have actually led to the crash ... but, many in the comments are shooting him down -- saying this is a very normal distance for these crafts to fly from one another.

As we told you ... an American Airlines jet collided with a Blackhawk helicopter near Ronald Reagan Washington National Airport -- and, video captured the explosion above the Potomac River.

As of this morning, 30 bodies have been recovered ... and D.C. Fire and EMS Chief John Donnelly said, "We don't believe there are any survivors." 60 passengers and four crew members were on the commercial flight, and three military personnel were on the helicopter.

A full investigation is underway ... and, distance like the one shown in this clip will almost certainly be scrutinized.