All four crew members have ejected safely after two Navy jets collided and crashed during an air show in Idaho.

The collision on Sunday at the Mountain Home Air Force Base involved two US Navy EA18-G Growlers from the Electronic Attack Squadron 129 in Whidbey Island, Washington.

The aircraft were performing an aerial demonstration when the crash happened. The four crew members from both jets safely ejected and were being evaluated by medical personnel. The crash was under investigation.

Nobody at the military base was hurt, said Kim Sykes, marketing director with Silver Wings of Idaho, which helped to plan the air show.

"Everyone is safe and I think that's the most important thing," Sykes said.

The base said in a social media post that it was locked down following the incident.

Videos posted online by spectators showed four parachutes opening in the sky as the aircraft plummet to the ground near the base about 80km south of Boise.

Organisers said the popular air show that includes flying demonstrations and parachute jumps is a celebration of aviation history and a look at modern military capabilities. The US Air Force Thunderbirds demonstration squadron headlined the show both days.

This year's Gunfighter Skies event was the first at the base since 2018, when a hang glider died in a crash during an air show performance.

In 2003, a Thunderbirds aircraft crashed while attempting a manoeuvre. The pilot, who was not hurt, was able to steer the plane away from the crowd and eject less than a second before it hit the ground.

The air show industry has been working to improve safety for years at the 200 events held each year in the United States.

The last fatal crash at an air show came in 2022 when two vintage military planes collided at an event in Dallas and killed six people.

Investigators may be able to quickly get an idea of what happened in Sunday's crash because the crews of both planes survived and will be able to tell investigators what they experienced before the collision.