We think we're starting at about the right time to skip straight to aviation hydrogen. Several companies are working on fuel cells and infrastructure specifically for aviation. We're starting with the battery version, and by the time we deploy the hydrogen version in the middle of the decade we expect the cost to have come down a lot.

If we're successful, these airships will be flying for decades to come. The extreme weather this summer and the recent IPCC report has driven home how important it is for new forms of transportation to be zero emission from the beginning.