After being inactive for two months, Amazon’s drones are once again taking to the skies.

Amazon confirmed to CNBC on Monday that it will resume Prime Air drone deliveries in the two U.S. areas where it is testing the service: College Station, Texas, and Tolleson, Arizona.

Amazon stopped drone deliveries in the two states in January after detecting issues with the altitude sensors of its 80-pound MK30 drones. Dusty air in the two cities had the potential to interfere with the drone’s altitude readings, creating a safety risk.

Amazon said on Monday that it did not experience any safety incidents in flights from the altitude sensor, but it took the precaution of stopping deliveries until it had rolled out a software update to fix the issue. As of last week, Amazon completed the update and received a stamp of approval from the Federal Aviation Administration to resume operations.

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Amazon spokesperson Av Zammit told CNBC that after getting back in the air, Prime Air drones had experienced “unprecedented levels of demand” from customers.

The drones are also getting packages to shoppers quickly. Prime Air’s Vice President and General Manager David Carbon shared on LinkedIn last week that a drone in Arizona was able to quickly deliver an order of ZzzQuil to a customer’s door in 31 minutes and 30 seconds. Carbon did not specify the distance the drone traveled.

Amazon stated on Monday that its MK30 drones had completed over 5,000 test flights and spent more than 900 hours in the air. Amazon touted the drone’s quieter flight and ability to travel longer distances than previous drones.

Because of that testing, the company wrote that it had “complete confidence in the underlying safety of the drone.”

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Amazon first showed its drone business to the public over a decade ago in December 2013 when founder Jeff Bezos revealed that Amazon was working on drones that would deliver packages to customers quickly.

Now, Amazon offers about 60,000 products for drone delivery for locations near its testing sites, with each product weighing five pounds or less and able to fit into a standard Prime Air box, per The New York Times. Amazon states that customers who live within its testing site range can have packages delivered in less than an hour.

Amazon’s drone delivery business is third in scale to the startup Zipline, which delivers for Walmart and will soon be delivering food for Chipotle, and Alphabet’s Wing service, which also delivers from Walmart to nearby areas, per The Wall Street Journal.

Amazon has delivered thousands of packages so far in Texas and Arizona, to deliver 500 million orders through drones every year by 2030.

Despite high demand, neighbors might not be so thrilled. In August, NBC News reported that residents of College Station, Texas, were complaining about the noise levels of the drones, which they said sounded like “chainsaws” and “a hundred swarms of bees.”