LOS ANGELES—A construction milestone was reached Thursday at the California Science Center, as the highest beams were raised into place on a future exhibit hall that will house the upright, launch-ready display of the space shuttle Endeavour.

Construction crews and Science Center officials took part in a “topping-out” ceremony Thursday morning, marking a major step toward completion of the Samuel Oschin Air and Space Center.

“Today we take a substantial step toward realizing the vision for the Samuel Oschin Air and Space Center, which will be a launch pad for creativity and innovation and inspire the next generation of scientists, engineers and explorers,” California Science Center President/CEO Jeffrey Rudolph said during the event.

The final beams raised into place Thursday were signed by members of the construction team, CSC officials and others involved in the ambitious project that will dramatically expand the size of the Science Center.

The $400 million, 200,000-square-foot Samuel Oschin Air and Space Center will nearly double the Science Center’s educational exhibition space. The building will include three multi-level galleries, themed for air, space and shuttle. The new facility will also house an events and exhibit center that will be home to large-scale rotating exhibitions.

The highlight of the center will be the Endeavour, which will be on display in a one-of-a-kind launch-ready vertical display. The 122-foot-long shuttle was lowered into position in the display earlier this year, joining with a pair of solid rocket boosters and a 65,000-pound external fuel tank known as ET-94.

The overall display is more than 20 stories tall, and it will be completely enclosed within the Samuel Oschin Air and Space Center.

The Endeavour had been on display horizontally at the Science Center for more than a decade.

In addition to the new center’s shuttle gallery, the building will also include the Kent Kresa Space Gallery and the Korean Air Aviation Gallery.

The Korean Air Aviation Gallery will include a collection of about 20 aircraft, some displayed on the ground and others suspended in the air. Among the aircraft on display will be a replica of the Wright Brothers’ 1902 Glider; a Harrier T4 jump-jet; a historic F-100 Super Saber; and the forward 50 feet of a Korean Air-operated Boeing 747 commercial airliner fuselage.

The Kent Kresa Space Gallery will examine how the machines built to explore space extend our reach and help transform our ideas about the universe and Earth. The gallery’s three prominent thematic areas will include Lift Off, Robotic Spacecraft and Telescopes, and Humans in Space. The center’s collection will showcase examples of spacecraft from every stage of the U.S. human space program, including flown space capsules: the Mercury MR2, Gemini 11, and Apollo-Soyuz Command Module; along with an array of engineering models of planetary probes, telescopes and Earth observation spacecraft.

An opening date for the center has not been announced.