Remember when Amazon announced Prime Air drone delivery back in 2013? Following the excited hubbub, other services including UPS scrambled to try out competitive airbone services. But then everyone ran into a slew of logistics and regulations issues, which have taken years to untangle. In the past few months, Google was given FAA approval for drone deliveries and Amazon might bypass regulation entirely for its air shipping. But UPS is going in a different direction: Testing UAVs to ferry emergency medical supplies.

Newly revised federal aviation regulations don't permit commercial drones to fly over people not involved in their operations and require them to remain within line of sight of their operators, effectively rendering commercial deliveries impossible. Drone-makers are working with regulators to tweak existing rules.