Rep. Rick Larsen (D-Wash.) acknowledged "responsible and safe" private drone users during a hearing on drone safety Wednesday, but also expressed concerns regarding how these aircrafts will avoid the path of airplanes. (CSPAN)

With airline pilots reporting close encounters with unmanned drones more than three times a day, it’s just a matter of time before a midair collision could carry deadly consequences.

That was the virtual consensus on Capitol Hill on Wednesday as lawmakers, pilots, experts and the Federal Aviation Administration gathered to discuss how to keep millions of privately owned drones out of the path of airplanes that carry millions of passengers.

“Unless more is done, it’s not if an accident will happen, it’s when,” Rep. Rick Larsen (D-Wash.) said at a hearing of the House subcommittee on aviation.

“We don’t really know what happens when you suck a quadcopter [drone] into a jet engine,” said Rep. Peter A. DeFazio (D-Ore.), who pointed out that a four-pound bird hits a jet moving at 260 mph with the force of 12 tons.

“When it hits one,” said Tim Canoll, president of the Air Line Pilots Association, “for the flight crew, it’s going to be a challenge to save the aircraft.”

That comment captures the urgency expressed at the hearing as the committee and the FAA look to protect people who fly and to encourage a commercial drone industry valued at $2.5 billion worldwide last year and expected to sell between 700,000 and 1 million units in the United States during the holiday season.

FAA Deputy Administrator Michael G. Whitaker told the committee that pilots report close brushes with drones about 100 times a month.

“We want people to enjoy this new technology, but we want to make sure that they do it safely,” Whitaker said. “Our preference is for people to voluntarily comply with regulations, but we won’t hesitate to take strong enforcement action against anyone who flies an unmanned aircraft in an unsafe or illegal manner.”

He said the FAA had investigated several hundred encounters and fined more than 20 drone operators, most recently Tuesday, when Chicago-based SkyPan International was hit with a proposed record fine of $1.9 million for 65 flights in the heavily trafficked skies over Chicago and New York.

“It’s almost inevitable that we’ll have a drone hit an aircraft,” said Rep. John L. Mica (R-Fla.), who criticized the FAA for moving too slowly with regulations.

Regulators face a challenge in identifying the operators of drones because the devices can be dispatched from and returned to fairly distant locations. There was general agreement among committee members and panelists that drones capable of more ambitious flight should be required to be registered, either with the government or on a manufacturer’s database that the FAA could access.

Stanford University aeronautics professor Mykel Kochenderfer suggested that, in most cases, drones should be prevented from flying above 400 feet.

He said a system such as the traffic collision avoidance system used by commercial airlines would require that drones be equipped with transponders, which are too heavy and too much of a battery drain for most drones to carry. He said lighter transponders are in development.

There also were suggestions that drone use be banned within a radius of large and mid-size airports — Rep. John Garamendi (D-Calif.) said two miles sounded right — or that technology be used to detect transmissions between a drone and its operator.

The FAA in February released proposed regulations for drones’ weighing less than 55 pounds. They require that the devices remain within the operator’s line of sight, cannot operate above anyone not involved with drone operation, can be used only during daylight hours, must yield right of way to other aircraft, can’t move faster than 100 miles per hour or at above 500 feet, and that an operator must contact air traffic controllers if operating in airspace they control.

Whitaker said he expects the rules to take effect next year.

Rich Hanson, a director of a group of model-aircraft hobbyists, said most of his 180,000 members understand the need for registration of certain drones.

“People get into this hobby, at least traditionally, because of their interest in aviation and their interest in learning how to build and operate their aircraft,” Hanson said. “The newer [drone] communities are attracted more by the technology and something it can do, such as taking pictures. They look at it as just an extension of their camera.”