Austin Butler, Callum Turner talk World War II miniseries 'Masters of the Air'

Austin Butler and Callum Turner lead an all-star cast of actors telling the stories of real-life heroes in "Masters of the Air."

Butler and Turner star as Major Gale "Buck" Cleven and Major John "Bucky" Egan, commanders of the 100th Bomb Group during World War II, on the new Apple TV+ miniseries from Steven Spielberg, Tom Hanks and Gary Goetzman.

Both actors told "Good Morning America" they were drawn to the project due to that trio of executive producers, the same team behind "Band of Brothers" and "The Pacific," with Butler saying it was a "no-brainer" decision to join and Turner calling it "just an honor to get to work with them and be in their orbit."

The miniseries explores the story of the men who made up the 100th Bomb Group, nicknamed the "Bloody Hundredth" due to the staggering losses they suffered, and features Tony nominee Anthony Boyle, Oscar nominee Barry Keoghan, "Doctor Who" star Ncuti Gatwa, Raff Law, Sawyer Spielberg and many more in its cast.

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"The honor I feel that I got to represent them is through the roof," Turner said of telling this story. "What these men did for us, they saved the world, and we wouldn't be living the way that we are if it wasn't for them."

Butler added, "The more that I learned about them and how brave and heroic they really were, they are true superheroes, and I just feel so privileged to get to bring their stories to life."

Keoghan, who plays Lt. Curtis Biddick, praised the entire cast's bond.

"You put a group of lads [together] and it could go either way," he said, "In terms of brotherhood, we connected, there was no ego ... it was all just support and being there for one another."

"I know I didn't walk into my first project and it been a Steven Spielberg one so … I couldn't even relate," he joked. "I was always there if anyone needed an ear or a bit of advice."

Law, who plays Sgt. Ken Lemmons, said the cast "bonded really naturally from day one" and credited the boot camps they went through to train for their roles with cementing that sense of camaraderie.

"I think it's really vital to the series that we did that, and those bonds were true," he continued. "They were real. Everyone got on so well and had each other's backs."

Law added, "I think it's important to show … the human side of these heroes as well, because not only were they very brave flying these missions, but they were young men … and they had friendships, they cared about each other, they had people back home, and I think that it's really important to get that balance across."

Inside Butler and Turner's on-set bromance

Goetzman said in casting Butler and Turner he, Spielberg and Hanks were "definitely looking for guys that we felt represented Cleven and Egan, but what was important was how they would get along, what would their chemistry be -- and these boys, quite frankly, have chemistry with about anybody in the world."

"They're really just great guys. Put them together and they're great guys with each other," he added. "They really are something special."

Butler and Turner were quick to sing each other's praises, too.

"I'm such a big fan of Austin," Turner said of the Oscar nominee. "I very genuinely think he's one of the best actors that we've got and I loved working with him. I learned so much as an actor [from him]."

Turner continued, "I know he'd come from 'Elvis' and he played this character that was full of energy, and then to come here, he just just completely transformed into someone else, man. Watching him be able to convey emotions just with a look and with a body shift is just beautiful. I loved every second, man, I really did."

Butler echoed Turner's sentiments, calling him "the best sparring partner I could have ever dreamed of" and an actor with "such power and gravitas."

"We talked a lot about the yin and yang of Cleven and Egan, so while there were moments where I was there and my job was sort of to settle into stillness, I then got to be there in support of watching Callum. It was so fun to watch because he would try different things every take, and to watch that freedom, it was really inspiring," he said.

Turner credited his co-star for giving him a "safe space" to explore his character, adding, "The truth is that I wouldn't have been able to do -- and have the confidence to do -- what I was doing if it wasn't that I was working with Austin."

"Masters of the Air" premieres Jan. 26 on Apple TV+.