A number of drones, like the Draganflyer X6 drone pictured, are in use by organizations ranging from local law enforcement to Customs and Border Patrol. (Mesa County Sheriff's Unmanned Operations Team/AP)

Before the low hum of drones appear above American homes, there will come ever-louder tones from defense and aerospace industry lobbyists pushing federal officials and lawmakers to bend to their firms' wishes.

In February, Congress mandated the FAA create rules to guide domestic drone flights, clearing the way for what industry executives are betting will be a new revolution in American aerospace history. If the agency completes the guidelines, unmanned aircraft could be approved for use by private operators and law-enforcement agencies in a few years.

But before defense and aerospace firms can cash in on their expected revolution, they have some work to do.

"There is a major battle brewing over how the FAA writes these regulations for domestic drone flights," says Alex Bronstein of First Street Research.

That fight will cover what the regulations stipulate about where and what for purposes drones can operate. The federal rules also will feature provisions mandating each unmanned aircraft meet certain safety specs—and the safer aircraft have to be, the more expensive they are to build.

Once the FAA completes the rules, engineers will handle the heavy lifting on developing drones that are suitable for civil use. But high-paid and well-connected Washington lobbyists are up first, charged with convincing FAA officials—and interested lawmakers—to write the regulations in ways that will allow firms to maximize their profits.

"Real power players of the defense industry have jumped out of the gates lobbying on this issue," says Bronstein, pointing to financial disclosure data showing military contractors like Raytheon, Bell Helicopter Textron and General Atomics have stepped up their lobbying efforts.

"These are big time heavyweights in the lobbying industry," says Bronstein.

"In this day of defense budget cuts, this is one of few emerging markets for these companies," says Bronstein. "We can draw the conclusion that since this sector is growing, the domestic drones will be a bigger focal point for their lobbying."

The firms that appear most interested in cashing in from selling unmanned aircraft to the Department of Homeland Security, state governments and local police departments have well-oiled lobbying outfits.

"General Atomics and Northrop Grumman are the dominant players in the unmanned aircraft business, and their products are better suited to civil or commercial missions than those of other companies," says Loren Thompson of the Lexington Institute and a defense industry consultant. "Lockheed Martin makes high-end unmanned systems, but they are too secret to use in most civil applications. Textron's smaller unmanned systems may have civilian uses."

As the battle heats up, it is unclear whether the FAA has a firm grasp of the information tidal wave coming its way, or the ability to separate facts from what would be best for shareholders and executives.

"This is not something the FAA is accustomed to," says Bronstein.

First Street Research released a report this week listing firms that have applied for authorization to operate drone aircraft in the U.S. skies. The report also highlights how much those firms spent during 2011 to lobby government officials.

Raytheon topped the list, spending nearly $7.4 million on lobbying. Next is Honeywell, which devoted nearly $7 million to the politics of persuasion. Bell Helicopter Textron and L-3 were next, spending $4.6 million and $3.8 million respectively on lobbying. General Atomics also wants drone-flight permission, and spent $2.3 million on lobbying efforts.

"It's hard to say how much of that was spent just on the domestic drones issue, because that's not how disclosure laws are written," Bronstein says. "But given the business opportunity and how important these regulations will be, we now it's going to increase. And it's going to increase in a big way."

John T. Bennett covers national security and foreign policy for U.S. News & World Report. You can contact him at jbennett@usnews.com or follow him on Twitter @BennettJohnT.