WEATHERFORD, Okla. (AP) — A popular space museum in Weatherford is expanding.

Construction has started on a 20,000-square-foot addition at the Stafford Air & Space Museum, The Journal Record reported. The museum's existing 42,000 square feet will be renovated as well.

The $5.4 million project will result in about 400 new exhibits at the museum, said Max Ary, museum director.

Ary said the museum has been working on the addition for almost two years. The expansion had to be large enough to fit two new, large items. A lunar space module, which stands two stories tall, and an F-117 stealth fighter jet are the main attractions in the addition.

The museum has worked for six years to get the F-117, Ary said. He said many people don't know that the museum's namesake, Lt. Gen. Thomas P. Stafford, spent several years helping to develop the advanced technology bomber as well as the stealth bomber.

Stafford, from Weatherford, is best known for commanding Apollo 10, which was the second manned mission to orbit the moon and the first to fly a lunar module in lunar orbit.

The museum's addition shell has been designed and will be constructed by Van Hoose Construction. MA+ Architecture firm has designed the building's interior, including the new exhibits.

MA+ Principal Architect Heath Tate and his team were already working on a Stafford-related project at Southwestern State University when they were asked to design the museum's new interior space. Stafford had donated his research materials to SWOSU, and MA+ was creating a space for them at the library.

Ary said he brought MA+ into the project when he was trying to find someone to create interior renderings for an upcoming banquet. SWOSU President and Stafford Museum board member Randy Beutler took the college's Stafford archive design to Ary. He said he was impressed with the work and they were invited to work on the addition's interiors.

MA+ Interior Designer Kalie Sheppard and Digital Artist Marty Law worked quickly to create renderings and a video for the gala, held May 18. Sheppard said Ary gave the team detailed artifact dimensions so they could create the spaces. Sheppard said this was a special project for her because she's from Weatherford.

Law said he's passionate about aerospace, so he was excited to work on the video. He said he's an Air Force brat, so he grew up going to aviation museums. He created his own models for the exhibits or purchased them from a stock image company.

"This was my dream project," he said. "It couldn't have been more in my wheelhouse," he said.

With MA+ working on the museum addition and the library archives, Ary said there's now continuity between the facilities. When construction is finished, the exhibit work will begin. The museum will remain open while existing exhibits are being updated as well.

The exhibit work is expected to take a few years, but with aviation always advancing, Ary said there could be more to add later.

"In many ways, I hope the building is never finished," he said.