Lithium Batteries on Airplanes: Rules for Passengers

DALLAS — International guidance for carrying power banks became stricter in 2026, but the central safety principle is unchanged: spare batteries belong where a developing problem can be seen and reached.

The International Civil Aviation Organization (ICAO) revised its Technical Instructions effective March 27. The new standard limits passengers to two power banks, prohibits recharging a power bank aboard the aircraft and recommends against using one to recharge another device in flight. How those provisions are adopted and enforced can vary by country and airline.

That international change also highlights why a simple instruction to “put lithium batteries in your carry-on” is incomplete. Rules differ for a loose battery, a power bank and a battery installed in a phone or laptop. They also distinguish rechargeable lithium-ion batteries from generally non-rechargeable lithium-metal batteries.

Why Thermal Runaway Is Different From an Ordinary Fire

A damaged, defective, overheated or short-circuited lithium cell can enter thermal runaway, a self-sustaining chemical reaction that produces rapidly rising heat and pressure. One failing cell can heat neighboring cells, causing repeated flare-ups along with smoke and flammable gases.

PHMSA describes thermal-runaway events as infrequent, but access matters when they happen. In the cabin, passengers or crew can notice warning signs and trained crewmembers can respond. A device inside checked baggage is more difficult to reach and cool. Class C cargo compartments on transport airplanes use fire detection and built-in suppression, but FAA testing found that halon does not stop thermal runaway and some lithium-battery scenarios can overwhelm those systems. The outcome depends on factors including battery chemistry, quantity, packaging and compartment design; one checked phone is not the same hazard as a bulk shipment of cells.

Carry-On and Checked-Bag Rules

Under current U.S. regulations, spare lithium batteries and power banks must be carried in the cabin. Each must be protected against short circuit. Travelers can keep batteries in their original retail packaging, cover exposed terminals with tape, or place each battery in a separate protective pouch or plastic bag.

A power bank counts as a spare battery because its primary purpose is to provide power to another device. If a carry-on bag is checked at the gate, remove power banks, spare batteries and charging cases before handing it over.

Devices with batteries installed are treated differently. Under U.S. rules, a compliant phone, laptop, camera or similar device may be packed in checked baggage, but it must be completely switched off—not left in sleep or hibernation mode—and protected against accidental activation and damage. The FAA recommends cabin carriage because the device remains accessible.

Damaged, defective, recalled or swollen batteries should not travel. The FAA says batteries or devices likely to spark or generate dangerous heat are prohibited unless the battery is removed or otherwise made safe. Swelling, unusual heat, odor, discoloration or leakage are warning signs, not cosmetic defects.

The 100 Wh and 160 Wh Limits

Lithium-ion batteries are regulated by watt-hours, or Wh. If the label shows volts and amp-hours, multiply those figures to find the rating. If it shows milliamp-hours, divide that figure by 1,000 before multiplying by the battery's nominal voltage.

For ordinary passenger use under U.S. rules:

• A lithium-ion battery up to 100 Wh does not require airline approval. A spare battery or power bank must be in carry-on baggage; a compliant installed battery may travel in the cabin or in checked baggage with the safeguards described above.
• A lithium-ion battery over 100 Wh through 160 Wh requires airline approval. A passenger may carry no more than two spares in this range, and only in the cabin.
• A lithium-ion battery over 160 Wh falls outside the ordinary passenger-baggage exception. Mobility aids and certain medical equipment have separate provisions, so travelers should contact the airline.

Airline and international policies can be stricter. Current U.S. rules and ICAO's 2026 addendum still allow a power bank over 100 Wh through 160 Wh with airline approval. IATA's 2026 operator guidance, however, presents a 100 Wh maximum ahead of a planned change to its 2027 Dangerous Goods Regulations. IATA is an airline trade body, not a national regulator, but its guidance is an important sign that a carrier may refuse an item permitted by the U.S. baseline. Check the operating airline before travel, especially on an international itinerary.

Lithium-metal batteries use another measure: grams of lithium content, not watt-hours. The ordinary limit is 2g per battery. The exception for batteries over 2g through 8g is narrowly limited to portable medical electronic devices, requires airline approval and permits no more than two such spares, carried with the portable medical device they are intended to operate.

Smart Luggage and Trackers

Smart luggage can contain a removable power source for charging devices, a motor or another feature. Under FAA smart-baggage guidance, a bag with a battery above the tiny 2.7 Wh lithium-ion or 0.3g lithium-metal tracker exception must remain in the cabin unless the battery is removed. If the bag is checked—including unexpectedly at the gate—the removed battery must be carried as a spare in the cabin.

A narrow exception allows a tiny installed battery of no more than 2.7 Wh lithium-ion or 0.3g lithium metal to remain in checked baggage. That accommodates compliant tracking tags; it is not permission to check an integrated power bank. Airlines may reject smart bags with non-removable batteries, so owners should confirm the carrier's policy before arriving at the airport.

What Crew Do When a Battery Overheats

Passengers who notice a device becoming unusually hot, expanding, smoking or burning should alert the crew immediately and should not try to move it. If a phone falls into a powered seat mechanism, do not adjust the seat; movement can crush the battery.

FAA cabin-fire guidance calls for crewmembers to knock down visible flames with an appropriate extinguisher and then immediately cool the cells with water, an aqueous agent or another nonalcoholic liquid. The first step suppresses flames; sustained cooling helps prevent the reaction from spreading between cells or reigniting.

That is why the familiar warning never to put water on any lithium battery is misleading in this setting. FAA guidance for trained crews specifically uses water to cool portable lithium batteries after flame knockdown. It also warns against covering a device, using ice or picking up a smoking or burning device.

Fire-containment bags are not a substitute for cooling. The FAA has no test standard or approval mechanism for those products and says an unstable or hot device should be cooled before it is moved. Passengers should stop using the device, avoid moving it and alert the crew.

A Preflight Battery Checklist

• Put power banks, charging cases and all spare or removed lithium batteries in carry-on baggage.
• Under the ICAO standard, carry no more than two power banks and do not recharge a power bank in flight. Check the airline's policy on using one to charge another device.
• Protect each spare battery's terminals from contact with metal objects or other batteries.
• Check the Wh rating and ask the airline in advance about any battery over 100 Wh.
• Remove a smart bag's larger battery before checking the bag and keep the battery in the cabin.
• Do not travel with a swollen, damaged, defective or recalled battery.
• Check the operating airline's rules shortly before departure because carrier and national limits may be stricter.
• Tell the crew immediately if a device becomes hot, swells, smells unusual, smokes or burns.