Why Are Lithium Batteries Restricted on Airplanes? Safety Rules Explained

Meta description: Learn why lithium batteries are restricted on airplanes, which batteries can go in carry-on or checked bags, and how to pack phones, power banks, and spare batteries safely.

Lithium batteries power phones, laptops, cameras, medical devices, and many other everyday items. They are also capable of overheating and catching fire if damaged, defective, short-circuited, or packed improperly. Because a battery fire can be difficult to control—especially in an aircraft cargo compartment—aviation rules limit where and how certain batteries may travel. Understanding the restrictions helps passengers pack safely and avoid delays at the airport.

Why Lithium Batteries Can Be a Fire Risk on Airplanes

Lithium-ion batteries store energy in rechargeable cells. Lithium-metal batteries, commonly found in some watches, cameras, and other devices, are generally nonrechargeable. Both types can pose a fire hazard if they fail, although the risks and applicable limits differ.

A serious failure can trigger thermal runaway: a chain reaction in which a cell overheats and releases energy, heat, and flammable gases. The heat can damage nearby cells and start a fire. A battery may enter this condition after physical damage, manufacturing defects, overheating, overcharging, or an electrical short circuit.

Aircraft add a particular safety challenge. A battery fire may produce intense heat and smoke, while confined spaces and limited access can make a fire harder to manage. In the passenger cabin, crew members can often identify a problem and respond. In a cargo compartment, a fire may be less visible and harder to reach directly. Fire-detection and suppression systems help, but they do not eliminate the underlying hazard.

Restrictions are therefore designed to reduce the likelihood of battery incidents and make potential emergencies easier to manage. They do not mean that every lithium battery is prohibited. Instead, rules account for battery type, capacity, quantity, placement, and whether the battery is installed in a device or carried separately.

Why Spare Batteries and Power Banks Belong in Carry-On Bags

In the United States, spare lithium batteries—including power banks—must generally be carried in carry-on baggage, not checked baggage. A power bank is treated as a spare battery because it stores energy and can supply power to another device. Spare batteries must also be protected from damage and short circuits.

A short circuit can occur when battery terminals touch metal objects, such as keys, coins, or another battery. Passengers can reduce this risk by keeping batteries in their original retail packaging, using a battery case, placing each battery in a separate plastic bag, or covering exposed terminals with tape.

Carry-on placement also gives the crew and passenger access if a battery overheats, smokes, or catches fire. The FAA advises passengers to tell a flight attendant immediately if a device or battery becomes hot, swells, leaks, gives off an unusual odor, or begins to smoke. A suspect battery should not be handled unless the crew directs it.

If a carry-on bag is taken at the gate and placed in the aircraft’s hold, passengers should remove spare batteries and power banks first. This matters particularly on full flights, when airlines may check larger cabin bags at the boarding gate.

Lithium Battery Limits for Passenger Flights

Battery capacity is usually measured in watt-hours (Wh). The limit depends on the battery’s chemistry and whether it is installed in a device or carried as a spare. The following table summarizes common U.S. passenger rules; airline policies and international regulations may add requirements.

For rechargeable lithium-ion batteries, the FAA’s general passenger limit is 100 Wh per battery without airline approval. Batteries above 100 Wh and up to 160 Wh may be allowed with airline approval, subject to quantity limits. Batteries larger than 160 Wh are generally prohibited in passenger baggage.

For lithium-metal batteries, the relevant measure is lithium content rather than watt-hours. Spare batteries are generally limited to 2 grams of lithium per battery. Small batteries in common consumer devices are typically below these limits, but unusual or high-capacity products should be checked with the airline before travel.

When a battery’s watt-hour rating is not printed on it, the value can sometimes be calculated from the label: watt-hours = volts × amp-hours. If the label gives milliamp-hours, divide that figure by 1,000 to convert it to amp-hours. For example, a 10,000 mAh battery rated at 3.7 volts has a nominal capacity of 37 Wh. Airline or manufacturer specifications should be checked when the battery label is unclear.

Carry-On Versus Checked Baggage

Passengers can generally bring phones, tablets, laptops, and other devices with installed lithium batteries in carry-on baggage. This is the preferred location because the device remains accessible if a battery problem occurs. The device should be protected from accidental activation, crushing, or damage.

Some devices with installed batteries may be placed in checked baggage under FAA rules, but they must be completely switched off—not left in sleep or standby mode—and protected from damage. Airline policies can be more restrictive, and certain devices or circumstances may have additional requirements. For the simplest and safest approach, passengers can keep battery-powered electronics in the cabin whenever possible.

Spare batteries and power banks are different: they generally cannot be placed in checked bags, even when packed safely. If a passenger has a spare battery that needs airline approval, approval should be obtained before arriving at the airport.

Smart luggage illustrates why battery placement matters. A suitcase with an installed lithium battery may be allowed as a carry-on if it meets airline rules. If the suitcase must be checked, its battery generally needs to be removable and carried in the cabin. A nonremovable battery can make the bag ineligible for travel, so passengers should check the manufacturer’s instructions and the airline’s policy.

Common Items That Require Special Attention

Power Banks and Portable Chargers

Power banks are spare lithium-ion batteries, so they belong in carry-on baggage. Check the Wh rating, protect the ports from metal objects, and follow the airline’s limits on quantity and capacity. A power bank should not be placed in a checked suitcase, including a bag checked at the gate.

Phones, Laptops, and Tablets

These devices are usually permitted when carried in the cabin. If they must be checked, they should be turned off completely and cushioned against impact. Passengers should not pack a device with a damaged, swollen, or recalled battery.

E-Cigarettes and Vaping Devices

E-cigarettes and vaping devices contain lithium batteries and are generally required to remain in the aircraft cabin. They must not be used or charged on the plane. Spare batteries also belong in carry-on baggage and must be protected from short circuits. U.S. Department of Transportation rules prohibit their use and charging aboard aircraft.

Medical Devices

Battery-powered medical equipment may be allowed, but the applicable rules depend on the device, battery capacity, and airline. Passengers using a portable oxygen concentrator, mobility aid, or other essential device should contact the airline well before departure to confirm approval, battery requirements, and procedures for travel.

Damaged or Recalled Batteries

A battery that is swollen, leaking, unusually hot, damaged, or subject to a safety recall may be unsafe to transport. Passengers should not assume that a battery is permitted just because it fits within the normal capacity limit. The FAA warns that damaged or recalled batteries may be restricted or prohibited; airline and manufacturer guidance should be followed.

What Happens if a Lithium Battery Overheats in Flight

If a phone, laptop, or other battery-powered device becomes unusually hot, starts smoking, or catches fire, passengers should alert a flight attendant immediately. Crew members are trained to respond to onboard battery incidents. Passengers should not hide the problem, put a smoking device in a bag, or pour water on it without crew direction.

For a device that is hot but not smoking or on fire, crew members may ask that it be disconnected from power and monitored. If a battery is actively burning, flight attendants follow their emergency procedures, which may include using appropriate firefighting equipment and cooling the device. The response depends on the situation; the crew’s instructions take priority.

Passengers should also avoid charging devices with damaged cables or unreliable accessories. Charging can generate heat, and a faulty connection may increase the risk of failure. If a device begins to swell, smell unusual, or behave abnormally before travel, it should be examined by a qualified service provider rather than packed for a flight.

How to Prepare Batteries Before Going to the Airport

• Check each battery’s rating. Look for watt-hours, voltage, amp-hours, or lithium content on the label or manufacturer’s product page.
• Pack spare batteries in carry-on baggage. This includes power banks and loose replacement batteries.
• Prevent short circuits. Use original packaging, a battery case, individual bags, or tape over exposed terminals.
• Protect devices from damage. Avoid packing electronics where they can be crushed or switched on accidentally.
• Remove batteries from gate-checked bags. Keep them with the passenger in the cabin.
• Ask the airline about larger batteries. Batteries above 100 Wh may need advance approval, and carrier rules can differ.
• Check international and connecting-flight rules. Other countries and airlines may impose additional limits or different procedures.

Why Airlines and Countries May Have Different Rules

Federal aviation regulations establish core limits for hazardous materials on U.S. flights, but airlines may apply stricter conditions. Policies can vary for battery quantities, approval procedures, mobility equipment, smart luggage, and other specialized items. International flights may also be subject to the rules of other national aviation authorities and international standards.

That is why a battery permitted on one itinerary may require additional approval on another. The safest source for a particular trip is the airline operating each flight, especially when a battery exceeds 100 Wh, a device is medically necessary, or luggage may be checked at the gate.

Official Sources for Current Battery Rules

The FAA provides passenger guidance on PackSafe: Portable Electronic Devices and Batteries, including information about spare batteries, power banks, and battery capacity. The Transportation Security Administration explains screening considerations in its What Can I Bring? tool. The U.S. Department of Transportation also publishes requirements for battery-powered devices and e-cigarettes. Because policies can change and airlines may set stricter limits, passengers should verify the rules with their carrier before packing.