Investigators analyzing the black box data from the recently crashed aircraft have uncovered a significant discrepancy that could provide crucial insight into the cause of the tragic collision.

Initial findings from the investigation into the tragic collision between an American Airlines CRJ-700 jet and a U.S. Army Black Hawk helicopter near Washington, D.C., which claimed 67 lives, indicate a significant altitude discrepancy at the time of the accident.

According to the jet’s flight recorder, it was flying at roughly 325 feet, while the control tower’s data placed the helicopter at 200 feet. This 125-foot difference is now under scrutiny by the National Transportation Safety Board (NTSB) as they seek to understand its impact on the fatal incident.

Investigators are delving into the conflicting altitude readings from the recent midair collision, exploring several potential causes. They are examining whether there were errors in the reported altitudes, if the helicopter might have surpassed its maximum allowed altitude of 200 feet for its flight path, and the impact of the crew’s use of night-vision goggles.

Recorded alerts from air traffic control to both the helicopter and the airplane, along with the aircraft’s last-second evasive actions, are being analyzed to further understand the dynamics of the incident.

“That’s what our job is, to figure that out,” NTSB member Todd Inman said, according to DailyMail, showing some frustration with reporters pressing for details on the altitude discrepancies.