It will be years before drones routinely deliver paper towels, cereal, and screwdrivers to our doorsteps, if ever. For now, companies are testing whether the flying devices are up to the job.
United Parcel Service ramped up its efforts on Monday by using a drone to drop off a package at a home in a Tampa, Fla. suburb. Although it has tested drone deliveries previously, UPS’ latest was noteworthy because it used a custom electric van outfitted with a recharging station for the battery-powered drone.
Besides current regulatory hurdles, one of the problems limiting drone deliveries is that drones require a lot of battery power and therefore can only stay aloft for a limited amount of time before running out of power. Many drones can fly for only 20 to 30 minutes.
Get Data Sheet, Fortune’s technology newsletter.
Electric vehicle company Workhorse supplied UPS with the custom van, battery charging station, and drone for the delivery test, said John Dodero, vice president of engineering for UPS.
When the UPS driver approached the intended home for delivery, she parked the car, and then launched the drone from its roof. From there, the drone flew to the home based on a pre-programmed flight path, dropped off the package held inside a small cage, and then flew off to rendezvous back with the van—which had since been driven to a spot miles away.
The van’s roof opened and revealed a platform for the drone to land on. With the help of an on-board mechanism in the van, the drone was able to plug itself into the battery charger on the platform.
Dodero said he did not know what was in the package, calling it an “insignificant” detail. He joked that UPS employees “don’t look inside customers’ packages.”
It should be noted that this was not an actual delivery to a customer, but rather a demonstration of UPS and Workhorse’s technology. The two companies have previously performed similar tests involving the electric van and custom drone, but Monday’s test was the companies’ first public performance, Dodero said.
Dodero said the test was intended to show that UPS drivers could eventually use drones to handle more deliveries than they would otherwise be able to do using the traditional method of going house-to-house by truck. In the future, he said that it may be possible for drivers to stop at one house to make a delivery while sending a drone to make a delivery at a second nearby home. While drivers travel to their next location, the drone would follow them and meet them at the new spot.
“It makes the driver more efficient,” Dodero said.
Still, Dodero said UPS is a “long ways” from actually debuting working drone delivery systems on a wide scale.
“We are just learning about the technology,” Dodero said. “This is all about us seeing how the technology works.”
Besides technology, a major hurdle limiting drone deliveries is the financial viability, according to a recent Gartner report.
Dodero said that drone technology “will continue to evolve” and that the cost of drones capable of performing deliveries will eventually decline. For now, the company is more concerned about evaluating the technology with the hope of eventually working to use drones “in a cost-efficient manner.”
“The total cost of ownership is not known at this time for us,” said Dodero. “We are just seeing how the technology works.”
When asked what did UPS learn about the drone delivery system on Monday that it hopes to improve on for future tests, Dodero said the company wants “to make it work faster,” but he declined to elaborate. He conceded he was being “intentionally vague” and did not want to reveal more details.
Besides UPS, companies like Amazon (amzn, +1.35%) and Google (goog, +0.24%) parent Alphabet are also exploring using drones for deliveries. Like UPS, they occasionally stage big publicity events during which drones have delivered orders like burritos to customers.
Despite the staged deliveries, several drone analysts believe it will still be years before drones are routinely delivering packages to customers.