A drone flies at the International Consumer Electronics Show in January in Las Vegas. (AP Photo/Jae C. Hong)

In August, the Federal Aviation Administration missed a key deadline for developing rules for small commercial drones. That failure has infuriated businesses that want to test and use drones for delivering goods, monitoring crops and doing other awesome things. Some have even threatened to move their drone research overseas if they can't get permission to operate in the United States.

Now the agency says that because of the delay, it will also miss its original September 2015 deadline for final rules.

"We all agree that the project is taking too long," Peggy Gilligan, a top FAA safety official, told a congressional House panel Wednesday.

Gilligan confirmed that a "balanced" proposal on drones is under executive review. But once that proposal is published for the public's eyes, it could take months to arrive at a final set of rules. The result could mean years of additional delays, according to a Government Accountability Office official.

"The consensus of opinion is the integration of unmanned systems will likely slip from the mandated deadline until 2017 or even later," said Gerald Dillingham, the GAO's director of civil aviation.

Lawmakers pounced on the confession, with some, such as Rep. Tom Massie (R-Ky.), complaining that the process is moving at a "geological time scale."

Looks like U.S. businesses will have to keep waiting for the rules they've been demanding.