Since autonomous airships still can still ignite as they're loading or unloading, it may be worth filling them with helium, but I do think using hydrogen may be

Since autonomous airships still can still ignite as they're loading or unloading, it may be worth filling them with helium, but I do think using hydrogen may be more appropriate for Project Loon. Hydrogen could still be viable as long as the airship is designed so people won't be hurt even if it does ignite. For example, the cargo could be designed to have a low terminal velocity or a ballistic parachutes could be used.