Ammonia can be directly used as fuel to generate electric energy in a low-temperature direct ammonia fuel cell (DAFC), making the DAFC an attractive option for zero-emission transportation. However, with a high-performance and durable DAFC still to be demonstrated, and with the remaining need to identify a suitable first market, the introduction of this technology has been delayed so far. Here, we report a high-performance DAFC stack enabled by a hydrophobic spinel cathode, which achieves the best combination of performance and durability reported to date. Peak power density of 410 mW cm-2 and continuous operation for 80 hours at 300 mA cm-2 were achieved for the first time in 5 cm2 DAFCs, and then successfully scaled up to 50 cm2. Five such cells were assembled into a 75 W DAFC stack using graphite bipolar plates, demonstrating stack performance at the level expected from the single cell tests. The best combination of performance and durability for the single cell and, particularly, the demonstration of the world’s first DAFC bipolar stack, constitute significant milestones in the development of DAFC technology. We also performed an in-depth techno-economic analysis of a 2 kW, 10 kWh DAFC system serving as power source for drones. Based on the DAFC performance demonstrated by us to date, such system can be a competitive power source over hydrogen fuel cells and Li-ion batteries.