BOISE - Two small planes collided in central Idaho on Friday morning at the site of a backcountry fly-in, killing a 2-year-old boy and injuring three other people.

A single-engine Piper Tri-Pacer and a twin-engine Beechcraft Baron collided in flight at 9:50 a.m. at Johnson Creek Airport, a backcountry air strip near Yellow Pine, the Federal Aviation Administration reported.

The Valley County sheriff's office said witnesses reported the two planes were landing at the same time when one came down on top of the other and both crashed.

The 2-year-old boy was fatally injured and his father was taken by air ambulance to a Boise hospital, where he was listed in serious condition, the sheriff's office said. The family is from Utah, but their names were not released.

Two men in the lower plane, both from the Roseburg, Ore., region, suffered non-life-threatening injuries, according to the sheriff's office. They were taken to a hospital in McCall.

The planes' tail numbers haven't been released.

Johnson Creek Airport has a grass runway and is a popular spot for backcountry aviation enthusiasts seeking access to mountainous terrain near the Frank Church River of No Return Wilderness. The 3,400-foot runway, located at 4,933 feet above sea level, is surrounded by densely forested mountains.

The airport has been the site of numerous crashes, including accidents in 1996, 2000, 2002, 2003, 2005, 2007 and 2010, according to a review of National Transportation Safety Board records documenting mishaps at the field.

Friday's accident occurred during a national fly-in of backcountry enthusiasts that runs through Sunday. More than 70 planes were lining both sides of the 150-foot-wide strip.

The crash occurred near the north end of the landing strip.

The NTSB will be the lead investigator into the cause of the collision, the FAA said.

Mike Pape, the aeronautics division administrator at the Idaho Transportation Department, was also flying to the crash site Friday afternoon.

The agency oversees Johnson Creek Airport and 30 other state-owned backcountry airstrips. Johnson Creek is easily the state's most popular, said Mel Coulter, a spokesman at ITD in Boise.

"As with all of our backcountry air strips, it requires a different level of skills and confidence to fly in and out of" Johnson Creek, Coulter said.

The airport remains open, but there could be restrictions, he said.

Valley County Sheriff Patti Bolen, whose offices in Cascade are about 50 miles southwest of the crash site, said in a statement her agency received a 911 call just minutes after the two planes went down.

The Beechcraft Baron is a twin-engine piston aircraft capable of flying 236 mph. Piper Tri-pacers belong to a class of four-seat, high-wing aircraft built into the 1960s.