Beer delivery drones and tacocopters: For businesses, it's a future that can't come soon enough. The only thing holding them back? An old Federal Aviation Administration ban on the use of commercial drones in U.S. airspace.

Pressure has been building for months for the FAA to develop clearer regulations on small drones — the little quad- and octocopters that most hobbyists can operate freely today, but not companies. Now, more than two dozen industry groups are asking the government for an interim set of policies in advance of an official set of rules.

The coalition includes some of the most powerful lobbies in Washington, such as the National Association of Realtors (real estate agents have been using drones to take pictures of properties from the air), the Aircraft Owners and Pilots Association (AOPA) and the National Air Traffic Controllers Association. Other signatories include agricultural groups representing soybean, barley and canola growers. The letter also marks the first time the manned aviation industry has joined the unmanned industry to call for clearer rules.

"The current regulatory void has left American entrepreneurs and others either sitting on the sidelines or operating in the absence of appropriate safety guidelines," said the letter, which was addressed to FAA administrator Michael Huerta and a copy of which was obtained by The Washington Post.

With a safety assessment, U.S. Transportation Secretary Anthony Foxx can establish his own rules for drones weighing less than 55 pounds. The drone industry's leading group, the Association for Unmanned Vehicle Systems International, wants Foxx to do just that, taking advantage of his authority under Section 333 of the FAA Modernization Act.

Others, such as AOPA vice president of government affairs Melissa Rudinger, say the FAA could easily look to model aircraft or other communities for inspiration in designing interim rules.

"We've had modelers flying small, remotely piloted models for decades," said Rudinger, "and they have a set of standards that — again, they're not regulatory — but, for example, you can't operate within a few miles of an airport, and you have to operate at an altitude of 400 feet or less."

The Government Accountability Office does not expect the FAA to meet its August 2014 deadline for a rule on small drones, though it has set up several test sites around the country as part of a wider effort to integrate the technology into the national airspace. Nor does the agency consistently enforce the ban that's on the books. Last month, a federal court said the FAA couldn't penalize a filmmaker's attempt to film a commercial with a drone. The filmmaker, Raphael Pirker, is the only person to have been targeted by the agency for flying a drone commercially, despite the FAA's blanket ban on the practice.

More people are taking their drones to the sky for unauthorized use, according to Rudinger, a chaotic situation that has the manned aviation industry worried.

"We want the FAA do to something now because otherwise these guys will  continue operating 'illegally,'" she said. "We think these are legitimate airspace users, but we want them to integrate safely. We want to make sure our members are safe when they're flying their aircraft."

An FAA spokesperson said the agency still expects to publish the formal rule on small drones "later this year."

"The rulemaking is very complex and we want to ensure that we strike the right balance of requirements for small UAS to help foster growth in this emerging industry," the FAA said. "We are having regular conversations with a few distinct industries to see if we can expand authorized commercial operations for limited applications in very controlled environments."