ARAPAHOE COUNTY, Colo. (KDVR) — The National Transportation Safety Board said Thursday its investigation into Wednesday’s mid-air collision involving two airplanes near Centennial Airport could take a year or longer.

The two planes — a Cirrus SR-22 and a Swearingen Metroliner operated by Key Lime Air — were both cleared to land on parallel runways when they collided. Nobody was injured.

“When they said it was Centennial, I was like, ‘Yeah, I can see that,’ because it’s a very busy airport. There’s a lot of traffic in there and on a clear day, which it seems like it was, there’s going to be even more,” said Ed Coleman, aviation safety expert and director for Robertson Safety Institute at Embry-Riddle Aeronautical University. 

Coleman says NTSB investigators will look into a number of things throughout their investigation, including human elements.

“Everybody makes errors, but why did they make those errors? That’s the key part. If we can figure out why it happened, then we can hopefully prevent it from happening in the future,” Coleman said.

In a statement, the NTSB said the investigation will look at the people involved in the accident, the airplanes involved in the accident and the environment in which the accident happened. There are currently four NTSB investigators working on the accident investigation.

Coleman says much can be learned about how this investigation will move forward by looking at previous investigations. The NTSB recently wrapped up another midair crash investigation that spanned nearly two years.

Six people died in May of 2019 near Ketchikan, Alaska, after two sightseeing planes collided. The NTSB released its full findings in late April. In that case, investigators found that obstructed views and problems with a system that alerts pilots to nearby planes combined to cause the midair crash. 

The NTSB will release a preliminary report in the Centennial Airport case within the next 14 days. The investigation is expected to take between 12 and 18 months to complete.