Nine skydivers survive, as one pilot ejects and the other manages to land damaged plane after crash over Wisconsin

Nine skydivers and two pilots survived with only minor injuries after their planes collided in midair over Wisconsin.

Skydiving instructor Mike Robinson was at 12,000 feet (3,600 meters), just seconds away from his fourth and final jump of the day, when a second plane carrying other skydivers struck the aircraft he was in, sending them all tumbling toward the ground.

Officials with the Federal Aviation Administration (FAA) were investigating the cause of Saturday's crash near Lake Superior, FAA spokesman Roland Herwig said on Sunday.

Robinson, an instructor and safety adviser for Skydive Superior, said the skydivers had gone up for their last jump of the day and the two planes were flying in formation.

All the skydivers were instructors or coaches and had hundreds, if not thousands, of jumps under their belts. It was Robinson's 937th jump.

"We do this all the time," Robinson said. "We just don't know what happened for sure that caused this."

He and three other skydivers were in the lead plane. All four had climbed out onto the step at the side of the Cessna 182 and were poised to jump. The plane behind theirs had five skydivers on board, three in position to jump and two more inside the plane.

"We were just a few seconds away from having a normal skydive when the trail plane came over the top of the lead aircraft and came down on top of it," he said. "It turned into a big flash fireball, and the wing separated.

"All of us knew we had a crash ... The wing over our head was gone, so we just left," he said.

The three skydivers on the step of the second plane were knocked off by the impact, Robinson said, and the two inside were able to jump. The pilot of Robinson's plane ejected himself, and the pilot of the second plane landed his damaged aircraft safely at Richard I. Bong Airport, where it had taken off from.

Robinson, 64, watched as the plane he'd been in spiralled downwards and broke into pieces.

"Looking around, we're seeing the wing that came off. We're seeing it's on fire, and there are just parts of the airplane floating in the air with us," he said. "We were falling faster than those parts ... So the concern was we get away from the crash area."

Robinson said the skydivers had parachutes that allowed them to steer themselves away from the falling debris and towards the planned landing spot. They opened their parachutes between 3,000 and 5,000 feet and landed safely.

The pilot of the plane that broke apart used an emergency parachute that cannot be steered, Robinson said. He suffered minor injuries on landing.

Robinson said his group was lucky.

"It might have been a lot worse," he said. "Everybody, to a person, responded just as they should, including the pilots."

He said that as he was diving he grew concerned when he saw only one emergency parachute, meaning only one pilot had ejected. He was relieved to learn the pilot of the second plane had been able to stay with the aircraft and land it.

The National Transportation Safety Board did not return a message from the Associated Press seeking comment.