Yes, it is generally okay to bring batteries on a plane, but there are very strict safety regulations regarding where they are stored and what type they are. In 2026, the primary rule is that Lithium-ion batteries (the kind in your phone, laptop, and power banks) must be in your carry-on luggage and are strictly prohibited from checked bags. This is because lithium batteries pose a fire risk; if they "short-circuit" or experience "thermal runaway" in the cabin, the crew can use specialized fire extinguishers to put them out, whereas a fire in the cargo hold could go unnoticed until it is catastrophic. For portable power banks, most airlines limit you to a capacity of 100 Watt-hours (Wh), which is roughly 27,000 mAh. If your battery is between 100Wh and 160Wh, you typically need airline approval. "Dry cell" batteries like AA, AAA, or D cells are allowed in both carry-on and checked bags, but they should be kept in their original packaging or have their terminals taped to prevent short-circuiting. Always ensure your spare batteries are protected from contact with metal objects like coins or keys to prevent accidental activation or sparks during transit.