A concerning and unusual technical issue has emerged among some iPhone users, where device batteries appear to swell noticeably during commercial flights, only to return to normal once the aircraft lands. This phenomenon, reported by owners of newer models like the iPhone 15 and iPhone 16 Pro Max, raises questions about battery manufacturing and the interaction between consumer electronics and the unique environmental conditions of air travel. While seemingly rare, the potential risks associated with a swollen lithium-ion battery, especially in a confined space like an airplane cabin, make this a significant topic for investigation.
User Reports Detail Mid-Flight Battery Swelling
The issue first gained attention through user reports on online forums. One iPhone 16 Pro Max owner documented their experience with a photograph, showing the device's battery had swollen enough during a flight to detach the phone's back panel from its body. Remarkably, the swelling subsided and the panel re-seated itself after the plane landed. A separate report from an iPhone 15 user described a similar event occurring on two different flights, with the battery returning to normal each time upon landing. This user later had their battery replaced at an Apple Store, after which the problem ceased, suggesting the issue may be tied to specific battery units rather than a universal design flaw.
Reported Models Affected:
- iPhone 16 Pro Max
- iPhone 15
The Leading Theory: Cabin Pressure and Trapped Gas
Technical commentators and users have proposed a plausible explanation centered on cabin pressure. Commercial aircraft cabins are pressurized to an equivalent altitude of 6,000–8,000 feet, which is lower than the atmospheric pressure at sea level. The prevailing theory is that some lithium-ion batteries may contain minute, trapped gases from the manufacturing process. Under normal sea-level pressure, this gas remains compressed and undetectable. However, at the reduced cabin pressure of a cruising aircraft, the gas can expand, causing the battery to swell temporarily. This would explain why the swelling is reversible; as the plane descends and cabin pressure increases, the gas compresses again, and the battery returns to its original shape. The issue may be more pronounced on older aircraft with less consistent cabin pressure control.
Proposed Cause: Expansion of trapped manufacturing gas within the lithium-ion battery due to reduced cabin pressure at cruising altitude (equivalent to 6,000-8,000 ft).
Safety Implications and Recommended User Actions
A swollen lithium-ion battery is a known safety concern, as it can be a precursor to thermal runaway, leading to overheating, leakage, or even fire. The confined environment of an airplane makes this a particularly serious scenario. Experts and experienced users strongly advise anyone who notices their phone (or any device) swelling during a flight to immediately alert the cabin crew. Do not ignore the issue or attempt to hide the device. Furthermore, it is crucial to document the event with photographs. As one user reported, Apple Store staff initially dismissed the claim until visual proof was provided, after which a battery replacement was authorized. Such swelling can also compromise the device's water and dust resistance.
Key User Safety Advice:
- Immediately alert flight crew if swelling is observed mid-flight.
- Document the swelling with photographs for warranty/service claims.
- Seek a battery replacement, as the issue may compromise device integrity and safety.
Scope and Manufacturer Response
Current evidence suggests this is a rare occurrence, potentially affecting only a small batch of batteries where manufacturing tolerances allowed for gas entrapment. There is no indication of a widespread, systemic fault across all new iPhone models. As of January 3, 2026, Apple has not issued an official statement or recall related to this specific in-flight swelling phenomenon. The company's standard warranty and battery service programs would likely cover affected devices, especially if the user can provide evidence of the defect. For consumers, the reports underscore the importance of being aware of how electronic devices behave under different environmental stresses and knowing the proper safety protocols.