See our Datapoints blog post: Eyes in the Sky: Resources to Learn about Drones.

Use BCC Research.

• Search for drone, and you will find a report for Drone Technology and Global Markets, as well as reports that have chapters about drones.

In IBIS World Industry Reports, you will find a report for the Unmanned Aerial Vehicle (UAV) Manufacturing industry in the US. ProcurementIQ also includes a report for buyers of UAVs.

Use EMIS. Select Industry Analysis, then Global Industry Sources. Search for unmanned or drone to find relevant reports.

Also, try Marketresearch.com Academic.

• Search for drone. There is a report here titled: Commercial and Military Drones: Technologies, Solutions, Market Outlook, and Forecasts 2016 - 2021, as well as others.

Search Business Source Complete.

• Search for trade, academic, and news articles using keywords such as: drones OR uav OR unmanned aerial vehicles.

Also, see resources such as the FAA's Unmanned Aircraft Systems page, AUVSI (Association for Unmanned Vehicle Systems International) and UAVSA.