Joe Walker flies a North American X-15 to a record altitude of 106,010 meters (347,800 feet) on X-15 Flight 90. Exceeding an altitude of 100 km, this flight qualifies as a human spaceflight under international convention.

Joseph Albert Walker was an American World War II pilot, experimental physicist, NASA test pilot, and astronaut who was the first person to fly an airplane to space. He was one of twelve pilots who flew the North American X-15, an experimental spaceplane jointly operated by the Air Force and NASA.

The North American X-15 is a hypersonic rocket-powered aircraft which was operated by the United States Air Force and the National Aeronautics and Space Administration (NASA) as part of the X-plane series of experimental aircraft. The X-15 set speed and altitude records in the 1960s, crossing the edge of outer space and returning with valuable data used in aircraft and spacecraft design. The X-15's highest speed, 4,520 miles per hour, was achieved on 3 October 1967, when William J. Knight flew at Mach 6.7 at an altitude of 102,100 feet (31,120 m), or 19.34 miles. This set the official world record for the highest speed ever recorded by a crewed, powered aircraft, which remains unbroken.

Flight 90 of the North American X-15 was a research flight conducted by NASA and the US Air Force on July 19, 1963. It was the first of two X-15 missions that passed the 100-km high Kármán line, the FAI definition of space, along with Flight 91 the next month. The X-15 was flown by Joseph A. Walker, who flew both X-15 spaceflights over the Kármán line.

Human spaceflight is spaceflight with a crew or passengers aboard a spacecraft, often with the spacecraft being operated directly by the onboard human crew. Spacecraft can also be remotely operated from ground stations on Earth, or autonomously, without any direct human involvement. People trained for spaceflight are called astronauts, cosmonauts (Russian), or taikonauts (Chinese); and non-professionals are referred to as spaceflight participants or spacefarers.