I was at an airport with twenty minutes before boarding and a phone at twelve percent. The wall outlet was slow, and I was about to give up when a stranger next to me said, “Put it on airplane mode. It charges faster.”

He was right. Here is why it works and how to squeeze more speed out of any charger.

Why airplane mode speeds things up

Your phone is constantly doing stuff in the background, checking for signal, syncing apps, pushing notifications. All of that uses battery. When you turn on airplane mode, the phone stops hunting for cell and Wi-Fi signal, so the power coming in goes straight to the battery instead of running the phone at the same time.

The difference is real. It is not going to triple your speed, but it can shave a noticeable chunk off a charge, especially on an older phone.

More ways to charge faster

• Use the original charger or one that matches your phone’s fast-charge rating. A cheap gas station charger is often the bottleneck.
• Charge from a wall outlet, not a computer USB port. Wall chargers deliver more power.
• Turn off the screen and stop using the phone while it charges. Watching video while charging basically cancels out the gain.
• Take the case off if the phone is getting hot. Heat slows charging down.

The one caveat

Airplane mode means no calls and no messages while it is on. So this trick is for when you are about to board a flight, or you can afford to be unreachable for twenty minutes. For a quick top-up before you head out the door, it is perfect.

I use it every time I am in a rush now. Turn on airplane mode, plug in, let it be. The phone comes back faster and cooler.