Transport chief Mable Chan said on Friday most pilot projects in Hong Kong's first-ever low-altitude economy test run will be operated manually and within the line of sight.

The Low-altitude Economy Regulatory Sandbox trials will test airspace management, flight operations and emergency responses to support the use of unmanned aircraft.

The initial phase, comprising 38 projects, is set to begin next month at Science Park, Cyberport and on some outlying islands.

One project will be a food delivery test run between Science Park and Ma On Shan.

Chan told an RTHK radio programme that safety is the top priority, noting that drones are equipped with propellers and backup systems.

"Based on safety and risk-based principles, we will begin by operating gradually within visual range," she said.

"For future beyond line-of-sight flights covering longer distances, we aim to advance further based on flight data collected from line-of-sight runs and assessments of safety considerations.

"In terms of tech and innovation research, some laboratories at universities are currently developing safety features for these drones.

"They've developed various self-defence mechanisms for the drones.

"Also, when one drone is in operation, another drone will monitor it nearby at the same time."

Speaking on another radio programme, Chan said officials will study the possibility of developing a low-altitude economy in the Northern Metropolis.

The government plans to amend regulations to increase drone weight limits from 25 kilogrammes to 150kg to allow more advanced drones to carry heavier loads.