Soldiers using jetpacks to buzz above battlefields and slip behind enemy lines may soon be a reality.

The military’s research and development arm has asked companies to submit ideas for a “portable personal air mobility system” that could be used in military missions, urban combat, maritime operations, search and rescue, and special operations. The Defense Advanced Research Projects Agency, or DARPA, said it’s “interested in understanding the feasibility” of the technology and, as of Tuesday, is accepting proposals for a six-month trial.

Jetpacks, which have played a starring role in science fiction for decades, aren’t the only thing the agency is interested in testing. Its bid also lists “powered gliders, powered wingsuits, and powered parafoils,” either reusable versions or for one-time use.

“Systems may be air deployed to allow for [infiltration] to hostile territory, or ground deployed to allow for greater off-road mobility,” DARPA wrote in introducing the proposal on the federal government’s business contracting website. 

The military has long been interested in jetpacks. But its past attempts have crashed and burned. As early as 1959, the military tapped aviation companies to create a personal air mobility system using rocket packs. Other efforts followed in the 1960s, including a version called the “Jet Belt.” But the prototypes—expensive, clunky, and able to fly for only a few minutes—ended up being limited by the era’s technology. Efforts in subsequent decades didn’t do much better, even while popular culture kept the dream alive.

More recently, however, with advancements in 3-D printing and smaller, computer-controlled gas turbines, jetpacks and its close cousins are now more feasible. And the handful of startups focused on the technology have gained considerable momentum.

Gravity Industries, for example, has created a device called the Jet Suit, which has one large turbine worn like a backpack and two additional ones located near each of the pilot’s hands. The device can fly someone up to 85 miles per hour for up to five minutes.

The company has already used the Jet Suit, which costs $440,000, in a trial to shuttle paramedics up a mountain for emergencies and to taxi people onto an aircraft carrier. Meanwhile, the U.S. Special Operations Command is evaluating the Jet Suit as is the British Royal Navy.

Richard Browning, the founder and chief test pilot of Gravity Industries, said his company is interested in submitting a proposal to DARPA. But because the company is U.K.-based, it’s checking whether it meets the requirement that applicants have a certain amount of U.S. business (Gravity has a U.S. presence).

While weapons could be added to a Jet Suit, it doesn’t have to be “like something out of a Marvel comic,” according to Browning. Rather, the suit could be used to help save lives and create new ways of getting around.

“It is really easy,” Browning said. “People can learn to do this in half an hour, like a bicycle.”

There is no guarantee that soldiers will be using jetpacks in combat anytime soon. DARPA funds many technologies that are never widely deployed or that morph into something else. Its request for proposals specifically calls out that possibility, saying that “a wide variety of less critical use cases may emerge for commercialization including urban mobility or recreation.”

DARPA said any technology submitted must be able to fly a single operator at least 3.1 miles at low-to-medium altitudes. Additionally, its setup should take[1]  no more than 10 minutes, with only minimal tools. 

Any proposal that is quiet and doesn’t heat up too much is also of “particular interest,” presumably to better evade detection by enemies. It also must be simple enough to operate with “relatively little training,” DARPA said.

The agency is flexible when it comes to how the device is powered. The bid says that it could use “emerging electric propulsion technologies, hydrogen fuel cells or conventional heavy fuel propulsion systems,” as long as it can take off from anywhere without the help of wind or elevation.

The window for proposals closes April 20. Any winner will be paid $225,00 for the six-month trial, which could be extended to a second phase that pays $1.5 million.