The military wants one-hour global delivery. SpaceX thinks it can pull it off.

On June 8, 1959, the Navy launched a rocket carrying 3,000 letters from the submarine USS Barbero, floating off the coast of Florida. “Before man reaches the moon,” Postmaster General Arthur A. Summerfield predicted, “mail will be delivered within hours from New York to California, to England, to India or to Australia by guided missiles.”

“Missile mail” failed to take off, but the government never gave up on the notion of delivering cargo to far off places in record times. Now the military has asked two private companies, SpaceX and a consulting business called the Exploration Architecture Corporation, to analyze whether rockets could fling payloads far heavier than postcards around the globe, Army general Stephen Lyons announced at a virtual conference of the National Defense Transportation Association last week. The military’s workhorse cargo aircraft, the Boeing C-17 Globemaster, can fly a tank to Afghanistan in about a dozen hours, but rocket delivery would be far faster.

“Think about moving the equivalent of a C-17 payload anywhere on the globe in less than an hour,” Lyons said, according to SpaceNews.

Under the deal, known as a Cooperative Research and Development Agreement, the companies will volunteer their time and resources to work with the US Transportation Command—a military organization that coordinates the movement of weapons and other resources—to study whether rockets might join planes, trucks, and ships in the military’s fleet of transportation vehicles. Lyons suggested that SpaceX could launch a test flight as early as next year.

Rockets and war have long gone hand in hand. In fact, Nazi Germany used one of the first functional modern rockets, the V-2, to terrorize European cities toward the end of World War II. After the war, the USSR and the US raced to scoop up V-2 hardware and key German rocket scientists, acquisitions that would launch the space programs of both countries.

Now things have come full circle. Supported in part by NASA contracts and expertise, SpaceX has emerged as space powerhouse with a growing fleet of rockets capable of placing satellites into orbit and hurling cars toward Mars. To reach orbit a rocket must exceed 25,000 miles per hour (nearly three dozen times the speed of sound), and high above the Earth’s surface there’s no air resistance to slow it down. The bottom stages of SpaceX rockets generally land near their launch site, but there’s nothing stopping the company from bringing them down on a different part of the planet.

Lyons didn’t say which vehicle the military is eyeing for recruitment, but a 2021 demonstration could involve either the company’s Falcon 9 workhorse, or its Falcon Heavy powerhouse, both of which have already demonstrated multiple successful flights. The former can carry 50,000 pounds of cargo to orbit for $62 million, and the latter 140,000 pounds for $90 million, although those figures would likely depend on the flight trajectory. By way of comparison, the C-17 aircraft has a maximum capacity of about 165,000 pounds and has been sold to American allies for hundreds of millions of dollars.

Or the military could be waiting for SpaceX’s upcoming Starship launch system, a fully reusable two stage rocket capable of hoisting 220,000 pounds of cargo to orbit. The company has built a handful of bare-bones prototypes of the first stage, some of which have made small “hop” flights. Construction of the first prototype booster may begin this fall, but so-called “point to point” flight tests on Earth remain years away, according to SpaceX founder Elon Musk. He has claimed that Starship operational costs could be as low as $2 million per flight.

If SpaceX can make Starship a reality, they have big plans for the platform. While the rocket was designed primarily to fly passengers around the moon and to Mars, SpaceX president Gwynne Shotwell has said that the company also hopes to take advantage of what she calls the system’s “residual capacity” to transport passengers between continents on Earth. At a 2018 TED talk, she predicted that Starship would someday shuttle blast well-heeled travelers between most major world cities in 20 to 40 minutes.

“This is definitely going to happen,” Shotwell said.

Of course, the company has a lot of details—both logistical and engineering—to work out before it does. How will air traffic control adapt to a world with rockets blasting off as often as planes take to the skies? Can explosive spacecraft ever be made as safe as commercial aviation? How will passengers stomach accelerating to 25 times the speed of sound in a matter of minutes?

If SpaceX is serious about operating what amounts to a hypersonic airline, learning to moving cargo around the globe for a client with deep pockets and might be a logical first step. The company has been discussing the idea with the military since at least 2018, and now it seems like their pitch might have landed.

“I had no sense for how fast SpaceX was moving, but I’ve received their update and I can tell you they are moving very rapidly in this area,” Lyons said.