Video posted on social media showed a small plane come dangerously close to crashing into a Colorado mountainside.
The Federal Aviation Administration said it had launched an investigation into Thursday afternoon's incident.
The single-engine Cessna 152 was flying near Devil's Thumb when it stalled and descended, the FAA said in a brief statement. It landed safely at its destination.
Jason Dunn said in a Facebook post that he was hiking when he saw the plane come up the valley from the opposite side. He wrote that it was "clear the plane was struggling trying to clear the saddle."
"It was coming straight at us, and as a former licensed pilot, I was worried it would go into an aerodynamic stall," he posted. "Then it either did, or the pilot made a last ditch effort to turn the plane around in a dead end valley before crashing into the mountain (or us)."
In the footage, the plane is seen flying toward the ground before it quickly ascends.
The FAA said it is not yet known how many people were on board.
Greg Boom, the owner of Rocky Mountain Flight School, said the pilot had rented the plane through them. He said the aircraft was checked, there were no problems with it and the pilot was not injured.
"It’s a little scary to see," he said, adding that the pilot "is not going to be flying at the flight school anymore."