What happens if you don’t put your phone on airplane mode on a flight?

Since some planes were built before these became a thing, it took a while for the industry to make sure it was entirely safe to use them.

Now, you’ll even see iPads and tablets in the flight deck, which pilots and flight attendants use to store paperwork digitally. These devices have been tested to make sure there’s no interference.

But that hasn’t always been the case! In fact, back in 2011, some parts within specific models of flight deck screen on certain Boeing 737 aircraft proved to be susceptible to interference.

How’d we find out that specific combination of planes and monitors — and fix it? During the rigorous testing process to enable airlines to offer inflight internet, that’s how.

Part of that testing process is creating enough electromagnetic interference to represent an entire cabin full of devices of a variety of sizes, including some that are malfunctioning.

Pretty much every airliner-equipment combo operated by a major international airline has now been tested.

For years, safety regulators, airlines, aircraft manufacturers and everyone else in the industry has known that there are dozens of devices left out of airplane mode on every flight.

In a way, the fact that planes haven’t fallen out of the sky because someone left their Kindle on is the best demonstration that, for the most part, most devices don’t affect most planes.

But most isn’t good enough for aviation. Some folks don’t know that their Kindle even has 3G, or that the Bluetooth on their watch/headphones/other device counts as needing to be in airplane mode.

Some forget that they’ve packed one of those devices in the overhead bin. Some even blatantly ignore the rules, assuming it's not going to make their plane start to plummet. And it probably isn’t.

But aviation doesn’t work on probablys. One of the reasons why aviation is safer than getting in a car, or even just staying at home is that airlines and regulators work with an abundance of caution.