Amazon can finally test its latest Prime Air drones in United States airspace, thanks to a new approval waiver from the Federal Aviation Administration.

In a letter dated Wednesday, the FAA told Paul Misener, Amazon’s VP of global public policy, that Amazon may begin testing its latest models of drones provided they don’t fly higher than 400 feet or travel faster than 100 mph.

“We’re pleased the FAA has granted our petition for this stage of R&D experimentation, and we look forward to working with the agency for permission to deliver Prime Air service to customers in the United States safely and soon,” Misener told ReadWrite via email.

See also: Why Drone Regulations Are Taking Forever

Previously, when Amazon asked the FAA for an exemption to test its drones, the department took a year and a half to respond. By then, the specific model of drone the FAA had granted Amazon approval to test had long been obsolete.

The FAA was able to respond more quickly the second time around thanks to an internal loophole that allows it to quickly issue an approval if “it has already granted a previous exemption similar to the new request.

See also: Amazon’s FAA Exemption Doesn’t Make Prime Air Any More Real

While the waiver allows Amazon to test its latest drones with the FAA’s blessing, that still leaves the technology giant at square one. In February, the FAA unveiled a list of proposed rules that would govern unmanned aircrafts 55 lbs or under, and they would require all operators to have a pilot’s license and maintain “line of sight” during operation. It’s unlikely that Prime Air drones could deliver products while maintaining line of sight the whole time.

However, these proposed rules aren’t final. The agency is expected to bring them to a vote later in 2015. 

Photo courtesy of Amazon