Why GPS still works in airplane mode (and how Skyty uses that)
First flight after I’d installed Skyty on my phone, the woman next to me asked exactly the right question. Wait — if your phone is in airplane mode, how does that map work? I tried to give a one-sentence answer and ended up giving a four-paragraph one. Here’s the version I wish I had had on the spot.
Airplane mode disables transmitters, not receivers. GPS is a one-way receiver. It never sends anything to space.
What airplane mode actually does
Tap the airplane icon in iOS Control Center and three things happen:
- The cellular modem stops transmitting and goes idle.
- WiFi turns off (you can re-enable it manually — many airlines now allow this).
- Bluetooth turns off (also re-enable-able).
Notice what’s missing from that list: GPS. iOS Location Services keep running. The reason is simple — GPS is a receive-only technology. Your phone listens for timing signals from satellites in medium Earth orbit (around 20 200 km up) and computes its own position from the differences. It never talks back. There’s nothing to disable, because there’s nothing being transmitted.
Why airlines don’t care
Airlines were never worried about GPS. They were worried about active radios — cellular and WiFi — interfering with avionics. As avionics got better-shielded over the past two decades, even those concerns relaxed: WiFi above 10 000 feet is standard now, and several countries allow cellular in the cabin.
GPS was never on the list. If anything, the cockpit uses GPS — the same satellites your phone is listening to.
Why other apps fail anyway
If GPS works, why do most map apps go gray at altitude?
Because they need map tiles — the actual pictures of the map — and they fetch those over the network. With cellular off and no airline WiFi, there’s nothing to fetch. The blue dot (your position) keeps moving, but it’s moving across an empty canvas.
How Skyty side-steps the whole problem
Skyty bundles the entire world map inside the app as a single Protomaps PMTiles file (~46 MB). When your phone gets GPS coordinates, the app already has the map data on disk. No fetch, no spinner, no empty canvas.
Same trick for the things that would normally need a server:
- City names — bundled cities database, nearest-neighbor lookup runs locally
- Airports — full IATA/ICAO database, on-device
- Time zones — computed from coordinates with bundled boundaries
- Sun position — astronomical formulas, no API
- Terrain elevation (for AGL) — optional NASA SRTM pack downloaded once at home
The result: the moment you enable airplane mode, Skyty doesn’t notice. It was never asking the network for anything.
Try this on your next flight
Before take-off, open Skyty and confirm you have a GPS fix (the position should look reasonable). Then enable airplane mode. Watch the map for the next twelve hours. Spoiler: nothing changes.
That’s the whole pitch.