Most airlines restrict any battery larger than 100W. Since our HyperJuice battery is rated 99.9W, it just fits under regulations, so it is airline safe.
Size limits: Lithium metal (non-rechargeable) batteries are limited to 2 grams of lithium per battery. Lithium-ion (rechargeable) batteries are limited to a rating of 100 watt-hours (Wh) per battery. These limits allow for nearly all types of lithium batteries used by the average person in their electronic devices. With airline approval, passengers may also carry up to two spare larger lithium-ion batteries (101-160 watt-hours). This size covers the larger after-market extended-life laptop computer batteries and some larger batteries used in professional audio/visual equipment.