Even for the veteran stunt coordinator, it sounded over-the-top.
"It's one of those conversations where everyone looks at each other and goes 'oh f**k,'" Eastwood said. "And Tom smiles and says 'it's going to be fun.'"
Two months later, Cruise would be running atop the wing of an Airbus A400M, clutching its side as it rose into the sky above the Wittering airbase in Northern England.
But the scene, which has become the signature of "Mission Impossible: Rogue Nation" and viewed by millions on YouTube before the film's Friday release, almost never happened. Airbus rejected the ambitious proposal, Eastwood says, because the aircraft used in the scene is new and was still being tested.
Their counteroffer, according to Eastwood: "Maybe when it's stopped on the ground you can look out the window."
Cruise wasn't flashing that signature grin.
After brainstorming other options for the plane, Cruise told Eastwood "I just want to be on the outside of that plane, go back and pitch them again."
This time, Eastwood — a pilot himself — drew up plans that would ensure Cruise would face as little danger as possible. They included a plan for getting the star inside the aircraft in an emergency, which involved a safety harness worn under his suit and a special rig just inside the plane's door.
"We did a lot of tests with dummies and everything went according to plan," Eastwood said. "The next thing was the plane landed in England and they [Airbus] literally threw the keys at us and said, 'OK.'"
But all wasn't OK — yet. Cruise still had to act while braving 185-mph winds, turning even small particles into dangerous debris.
The actor was opposed to wearing goggles, which would prevent the fear in his face from coming through on screen. Instead, the crew put a protective coating over his eye balls, similar to thick contact lenses, keeping his eyes safe from small debris and allowing them to stay open through the punishing wind.
The next problem was Cruise's safety harness. Though it was keeping him alive, its constricting nature was preventing him from using his body to act.
"I feel like a puppet," Eastwood recalls Cruise saying. "I won't be able to sell the fear."
The crew added slack to the line, meaning that if Cruise lost his grip on the side of the plane he actually would have fallen several feet before the harness saved him.
"[In the scene] his feet slip off the plane and he really is holding on for his life," Eastwood said. The handles Cruise clutches are actually panels used to cut down on turbulence as paratroopers exit the military aircraft.
Confident that the stunt was as safe as possible, Eastwood says there was only one thing that still scared him: birds. No safety measure could stop a bird strike, but they minimized the risk by dispersing birds from around the airport and putting a spotter in the cockpit.
Then came the take-off, which posed another threat to Cruise. To get the shot the plane had to rise at an angle more akin to an airshow take off.
"The shot was far more effective seeing the runway shrink," Eastwood said. "This meant a high G-load on Tom," he added, referring to the gravitational force that adds weight and makes it harder to maintain balance.
Cruise and his crew repeated the stunt eight times to get the shots that made it into the film. No one was hurt, and Eastwood calls it one of his "all time greats."
But there was little time to celebrate. There were more stunts to come, like one that requires Cruise to hold his breath under water for six minutes.
"Time to start panicking about the next one," Eastwood said.