Ukraine has, for the first time, sent into combat a hybrid drone powered by hydrogen fuel. According to the builder Skyeton, a variant of its Raybird was deployed for full-scale combat duty with the Ukrainian Armed Forces in an active war zone.
Archived version: https://archive.is/newest/https://newatlas.com/military/world-first-ukraine-hydrogen-drone/
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Not necessarily because diesel can be at atmospheric pressure while hydrogen needs heavier containers to keep it pressurised and liquid.