Mike Robinson was at 12,000 feet, just seconds away from his last jump of the day, when a second plane carrying other skydivers struck the aircraft he was in, sending them all parachuting to the ground.

None of the nine skydivers or two pilots was seriously hurt when the planes collided Saturday evening in far northwest Wisconsin near Lake Superior. Authorities still didn’t know Sunday what caused the accident.

Robinson, 64, of Duluth, Minn., an instructor and safety adviser for Skydive Superior, said he and three other skydivers were in a lead plane Saturday and had climbed onto the step to jump. The plane behind theirs had five skydivers on board, three ready to jump and two still inside.

The three who were on the step of the second plane got knocked off on 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 the aircraft safely at Richard I. Bong Airport, where it took off. Robinson said the skydivers had parachutes that allowed them to steer toward the planned landing spot.

— Associated Press