ANCHORAGE, Alaska - Two small planes collided in midair along a narrow and treacherous mountain corridor in Alaska in a crash that marked an extraordinarily rare event: No one was injured.

"It is extremely unusual," Federal Aviation Administration spokesman Mike Fergus said Monday. "It is almost unheard of."

The near-tragedy occurred Sunday afternoon as a Piper Navajo and Cessna 206 floatplane were flying directly toward each other in Lake Clark Pass - a narrow river valley that runs between Anchorage mountains.

Radar is useless in the high-traffic corridor that is just a quarter-mile (400 meters) wide in some places. The nine people aboard the Piper Navajo and the four in the Cessna 206 floatplane had no idea they were about to collide in the passage.

The Piper had made a round of villages and was taking passengers to Anchorage. A family doing some bear viewing was traveling in the Cessna. Visibility at the time was excellent.

"One was coming northbound. The other was going south toward Port Alsworth and they just didn't see each other until the last second," said National Transportation Safety Board investigator Larry Lewis. "Neither made any evasive maneuvers as far as we can tell."

The Cessna was slightly higher than the Piper.

"He actually hit the top of the Navajo's tail with his floats," Lewis said.

The planes sustained some minor damage but were able to land safely in Anchorage.

The FAA's Fergus described it as one of the rarest of events, a midair collision in which no one was injured and the pilots were able to safely land at airports - the Piper landed at Merrill Field, its intended destination and the Cessna went to Lake Hood.

But Lelya Alsworth described it another way: "What a miracle."

Alsworth is married to the chief pilot of Lake Clark Air, which owns the Piper.

Lewis said it can be hard to see a plane coming head-on. Wings that are 300 square feet (28 square meters) are reduced to a 10-inch (25-centimeter) profile, he said.

"That is not much to see," he said.

The area is unregulated air space - like most of Alaska - where pilots must follow visual flight rules. Investigators will want to know whether the pilots were following the accepted practices, such as normally staying to the right side of the pass.

Lewis said the NTSB will examine the planes for damage Tuesday.

Both the NTSB and the FAA are investigating.