Erik Nelson describes his documentary “The Cold Blue” as “the garage band of movies” — he didn’t have the large team or crew other documentary contenders have.

“The Cold Blue” is a World War II documentary that looks at raids and B-17 bombing missions that took place during the war. Nelson’s team looked at 34 reels of 16mm footage from William Wyler’s “The Memphis Belle: A Story of a Flying Fortress,” poring over them for 15 hours.

The footage was without sound, so Nelson not only restored it to stunning quality, but he also tracked down eight of the existing B-17 planes, flew up in them and captured the sound. The end result is an immersive and modern documentary.

As a film historian, Nelson also sought out veterans who flew the B-17s.

“Wyler covered the bomb runs, the briefings, and I knew what we had,” Nelson said of the footage. “I wanted to ask what it sounded like, what it felt like and what it was like to do that.” Once he had his audio interviews, Nelson edited and wove the interviews into the restored picture footage.

David C. Hughes was the sound editor on “The Cold Blue.” He brought sound equipment from The Skywalker Ranch and spent four days recording the sounds of the B-17 planes. Later on, one of the planes the team had worked on crashed, and shortly after, a veteran that Nelson interiewed passed away.

“The veterans aren’t going to be here much longer. They are in great shape, but we still have to remember that. I felt an obligation (in making this) to preserve the past. It’s important to do so,” Nelson explained.

In addition to preserving the past, Nelson also wanted to let the storytelling do its work. “I was very conscious and wanted to create a time machine. So, you hear the voices of the veterans. You realize they were there. You’ve never seen the footage like this before. I wanted to be pure to the concept. There were no narration and no imposition from the director,” he said.

Specific details like how the men craved eggs for breakfast and what it was like to be on that bombing run are part of how Nelson preserved the past. The documentary pays tribute to the extraordinary filmmaking talents of Wyler, who also directed “The Best Years of Our Lives,” “Roman Holiday,” and “Ben-Hur,” and to his DP, who was killed during the bomb runs. The documentary serves as a chance to revisit Wyler’s restored footage in a new and modern way, with voiceovers from people who were there.