E-commerce power Amazon.com blasted federal regulators on Tuesday for being slow to approve commercial drone testing, saying the United States is falling behind other countries in the potentially lucrative area of unmanned aviation technology.

Less than a week after the Federal Aviation Administration gave Amazon.com the green light to test a delivery drone outdoors, the company told U.S. lawmakers that the prototype had already become obsolete while the company waited more than six months for the agency's permission.

"We don't test it anymore. We've moved on to more advanced designs that we already are testing abroad," said Paul Misener, Amazon.com's vice president for global public policy.