The troubled F-35 Joint Strike Fighter “almost certainly will be the last manned strike fighter aircraft the Department of the Navy will ever buy or fly,” Mabus declared.

To reinforce his position, Mabus created a new undersecretary post specifically for drones. The day after the X-47B showed off its new skills, the Navy held a conference to discuss ideas about the pilotless future with various companies.

According to briefing slides, the aviation industry needs to work on air-to-air refueling, advanced navigation systems, solar power and new lightweight materials. The Navy also wants GPS gear that resists jamming and hacking, better sensors and fancier communications relays.

While the Navy might continue tinkering with the X-47B, the pilotless jet was never intended for actual combat. The program’s official name—Unmanned Combat Air System Demonstration—and the so-called “X-plane” designation both highlight its experimental nature.

Eventually, the Navy wants to develop a new jet dubbed the Unmanned Carrier Launched Airborne Surveillance and Strike System—a.k.a. UCLASS. But the transition is slow and problematic despite enthusiastic support from Mabus.

In August 2013, the Navy announced that it had awarded contracts to Boeing, General Atomics, Lockheed Martin and Northrop Grumman to develop possible designs for the new UCLASS aircraft. Northrop Grumman proposed a new C-model X-47.

General Atomics — maker of the famed Predator and Reaper drones — developed a sea-going version of the company’s Avenger. The Lockheed Sea Ghost takes some cues from the firm’s top-secret RQ-170 “Wraith,” while Boeing derived its offering from the pilotless X-45 concept plane.

But even with these designs already in the works, the biggest issue by far is disagreements over just what the UCLASS is actually supposed to do.

Lawmakers worried that the Navy focused on making the drone an aerial spy with only a limited ability to blow things up—a kind of glorified Reaper.

“We believe the current path could limit the capability growth of the system in the future,” Reps. Randy Forbes of Virginia and Mike McIntyre of North Carolina wrote in a letter to Mabus.

The two sent the letter a month after the Pentagon handed out the contracts. The legislators wanted Mabus to make sure the drones could kill.

The Navy revised the UCLASS requirements. In April 2014, the sailing branch sent a classified set of design details to companies working on the prototypes.

According to the Navy’s latest budget request, the new and more complex UCLASS should do everything from “counter-terrorism operations”—likely akin to what Predators and Reapers do now—to “high-end denied operations”—missions over hostile territory full of surface-to-air missiles, enemy fighters and other hazards.

But not every lawmaker believes that the Navy’s new drone will be deadly. In March, Sen. John McCain, chairman of the Senate Armed Services Committee, sent a letter to newly appointed Secretary of Defense Ashton Carter reiterating fears about the Navy’s upcoming drone fleet.

“I am concerned that the current requirements proposed for the UCLASS program put a disproportionate emphasis on … ISR support,” McCain wrote, using the Pentagon acronym for intelligence, surveillance and reconnaissance. “I would encourage you to ensure that the Navy’s first unmanned combat aircraft is capable of … conducting strike missions.”

On top of that, “under current plans, starting this April, there will be no unmanned air vehicles operating from carrier decks for several years,” McCain warned. He encouraged Carter to keep the X-47Bs flying in the meantime.

Whatever the UCLASS does in the end, the Navy insists the pilotless planes will incorporate both new technology and the lessons learned from the X-47B. The Navy hopes to have the drones serving aboard carriers sometime between 2022 and 2032.