What happens if you don't use airplane mode on a plane? The US rules, explained

Most likely nothing dramatic, but in the United States using your phone's cellular connection in flight is prohibited by FCC and FAA rules, and on board the crew's instructions are the ones you have to follow. Airplane mode, or turning cellular off, is how you comply, and you can still use Wi-Fi if your flight has it.

What the rules actually say

• FCC: cell phones "must not be operated while such aircraft are airborne." The rule itself warns that a violation could lead to suspension of service or a fine. In 2020 the FCC dropped its long-running proposal to allow phone service in flight, so the restriction stands.
• FAA: on airline flights, only the devices the airline has approved may be used. The FAA's advice to passengers is plain: phones and other devices must be in airplane mode or have the cellular connection disabled. On the ground, the FAA allows cell phone use, subject to the airline's instructions.
• Crew instructions: federal rules prohibit interfering with a crewmember's duties. If a flight attendant asks you to switch to airplane mode, that's the request to follow.
• Calls: Congress has also told the Department of Transportation to write rules banning voice calls on mobile phones during domestic flights.

Is it illegal?

"Illegal" makes it sound like a crime. More precisely: using your phone's cellular connection while airborne breaks an FCC rule, which itself mentions suspension of service or a fine as possible consequences, and refusing crew instructions breaks FAA rules. The simple fix is airplane mode, or turning cellular off, from takeoff to landing.

Why the rules exist

The FAA's concern is interference with the airplane's navigation and communication systems, which is why each airline has to determine which devices can be used safely. The FCC's rule governs use of the cellular network from the air, and the FAA supports it in US airspace. Planes with installed Wi-Fi or approved onboard phone systems are built to tolerate devices connected to those systems.

What still works in airplane mode

Airplane mode switches off transmitters. GPS only receives satellite signals, so on most phones it stays available, though it struggles to get a fix inside the cabin. Read does GPS work in airplane mode?

Follow your flight in airplane mode

FlyingOver doesn't use GPS. Before takeoff it saves your route, schedule and an offline map; in flight, with your phone in airplane mode, it shows your plane's estimated position from any seat. See how to track your flight without Wi-Fi.