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What SpotFlight is

SpotFlight turns your iPhone into a finder for the sky above you. Point the phone at an aircraft and the live camera view labels it: callsign, aircraft type, altitude, distance, and — when it is known — where the flight came from and where it is going.

Three other views back it up. A map of the traffic around you, drawn with the exact cone your camera is currently covering, so you can see what you would catch if you turned that way. A nearby list, nearest first, with every number the data actually supports. And a search that finds one specific flight by flight number, callsign, registration, or ICAO address, and points you at it.

SpotFlight also predicts two things that are hard to catch by chance: an aircraft about to pass close overhead, and an aircraft about to cross the disc of the Sun or the Moon from exactly where you are standing.

Positions reach the app through my own relay, which keeps a snapshot of world air traffic in memory. That snapshot is itself built from free, community-run networks of volunteer ADS-B receivers, adsb.lol among them — and adsb.lol is also what the app falls back to if my relay is unreachable. Departure and arrival cities come from adsbdb.com. SpotFlight has no account, no subscription, no ads, and no analytics.

Requirements: iPhone running iOS 17.0 or later, an internet connection, and a view of the sky. Portrait orientation. SpotFlight runs on iPad in iPhone compatibility mode, but it is designed for the phone.

Frequently asked questions

I see no aircraft at all. What is wrong?

Work through these in order — one of them is almost always the answer.

1. Check your internet connection. SpotFlight has no offline mode. Every position is fetched live. 2. Check that Location is allowed. Settings → SpotFlight → Location → While Using the App. Without your real position, SpotFlight cannot ask "what is flying near here", and the aircraft you see will not be yours. 3. Open the Nearby tab. It shows a plain count and the age of the data in seconds. If Nearby has aircraft but the camera view looks empty, the problem is where you are pointing, not the data — see the next question. 4. Point higher. Cruising aircraft sit around 10–12 km up. If you are aiming near the horizon you are mostly looking at aircraft that are below it — SpotFlight draws those in orange and tells you they are hidden behind the curve of the Earth. 5. Consider where you are. Coverage comes from volunteers running receivers at home. It is dense over Europe and North America, thin over oceans, deserts, and sparsely populated regions. Low-flying aircraft are often invisible even in well-covered areas, because ADS-B reception is line of sight. 6. Check the time of day. At 4 a.m. over a rural area there may genuinely be nothing up there.

If Nearby shows a healthy count but you are certain the aircraft listed are not near you, your location is probably not being used — see point 2.

The aircraft is not exactly where the label says. Why?

Because your iPhone's compass is the weakest link in the chain, and this is worth understanding rather than working around.

The maths behind SpotFlight is precise. It uses the WGS84 ellipsoid throughout, converts to an Earth-centred frame so the curvature of the Earth is exact rather than approximated, and corrects the two separate delays that every ADS-B position carries. Those errors are small.

The magnetometer in an iPhone is not. Depending on what is around you — a car, a steel railing, a balcony, a laptop, a magnetic case — heading error runs from about 5° to 15°. At 40 km, a 10° error puts the label about 7 km to the side of the aircraft. Every other error source in the app is orders of magnitude smaller than that one.

What this actually looks like on screen is not a lost aircraft. Tests measured it: a 5° error shifts a label about 15% of the half-width of the frame, and 15° shifts it about 46%. The aircraft stays in view. What you lose is the pairing — which label belongs to which dot.

So SpotFlight lets you fix it by hand, which is the reliable answer.

What is the heading nudge, and how do I use it?

Drag anywhere on the camera view. The whole overlay rotates with your finger, and a readout shows how many degrees of correction you have applied. Line the labels up with the aircraft you can actually see, let go, and everything else on screen — every other label, the horizon line, the viewing cone on the map — is correct from that moment on. A reset button clears the correction.

This is deliberate, not a workaround for a bug. No amount of software can recover a heading the magnetometer reported wrong; your eyes can, in about two seconds. One aircraft you can positively identify calibrates the whole sky.

Two things that help before you nudge: move away from metal and from your car, and if SpotFlight shows a calibration warning, wave the phone in a figure eight for a few seconds — that is iOS recalibrating the compass. The Settings screen reports the compass's own estimate of its accuracy, and what that error costs in metres at 40 km.

Why does a flight show no departure or arrival city?

Because that information is not broadcast by the aircraft. An ADS-B transponder sends position, altitude, speed, track, and a callsign — it does not send a route. SpotFlight looks the route up in a separate database, keyed on the callsign.

That database does not know every flight. Roughly a quarter of the aircraft you see will have no route: business jets, private aircraft, military traffic, ferry and positioning flights, and freshly assigned callsigns. SpotFlight treats routes as decoration, never as a requirement — when a route is unknown, the app simply shows nothing rather than guessing.

You can turn route lookups off entirely in Settings. With the toggle off, SpotFlight makes no requests to the route service at all.

Does it work offline?

No. SpotFlight needs a live internet connection, and there is no cached "last known sky". The positions are only meaningful while they are fresh — an aircraft at cruising speed covers about 250 metres every second, and SpotFlight discards any position it has not seen updated for two minutes rather than inventing where the aircraft might be.

Data use is modest: small JSON responses, no images, no video, no uploads.

Which aircraft are missing, and why?

Several categories, and it is better to know them than to wonder:

do not transmit ADS-B or transmit without a position.

receives are Mode S only, with no coordinates. They are discarded, and the Nearby tab tells you how many.

receiver with a view of that patch of sky — over the sea, over mountains, over empty country — the aircraft is invisible to the network no matter how well it is broadcasting.

small airfield are frequently below the receivers' horizon.

Registration and aircraft type are also occasionally missing from the broadcast itself. SpotFlight shows a blank rather than a guess.

Is my location shared?

Your coordinates are sent to my relay — or to api.adsb.lol if it cannot be reached — and nowhere else, because they are the question being asked: "which aircraft are near this point?" There is no way to get an answer without sending the point. This happens roughly every five seconds while SpotFlight is open and in the foreground, and never in the background.

Everything else is a no:

that could tie them to you.

There are none in the app at all — it is built entirely on Apple frameworks.

provides a live backdrop and reports the lens's true field of view. Nothing is photographed, analysed, or stored.

receiving location as soon as you leave the app.

routes on/off), kept in the app on your phone.

SpotFlight talks to three servers. Positions come from my relay, spotflight.ftso.paris, and from api.adsb.lol if the relay cannot be reached; route cities come from api.adsbdb.com. The last two are free community services run by other people. As with any website you visit, all three see the request and the IP address it came from — but mine records neither that address nor your coordinates, which is set out precisely in the privacy policy.

How do the Sun and Moon transit predictions work — and is it safe?

Safety first: never look directly at the Sun, with or without a phone in your hand. It can cause permanent eye damage in seconds. Watch the transit on the screen, with the phone held between you and the Sun so the Sun itself is out of your line of sight. It is also sensible not to leave the camera aimed at the Sun for minutes at a time.

How it works: SpotFlight computes where the Sun and the Moon are from your exact position, extrapolates each aircraft forward along its current track, and looks for the moment the two directions coincide. It searches up to five minutes ahead, recomputing every ten seconds, and tells you when to look, where to look, and how long the crossing will last. It also distinguishes a true transit — the aircraft actually crosses the disc — from a near miss, by angular separation.

The astronomy has been checked against NASA JPL's DE421 ephemeris across five sites in both hemispheres and five points in the year: worst case 28 arcseconds of error for the Sun and 46 arcseconds for the Moon. The Moon's disc is about 1,860 arcseconds across, so that is roughly one fortieth of its radius. The Moon's position is computed for your point on the ground, not the centre of the Earth — at 384,000 km that difference is nearly a full degree, twice the Moon's own width, so it cannot be skipped.

Two honest caveats. First, be quick: an aircraft at 30 km crosses the Sun in about one second, and at 10 km in under half a second. Set up early and watch the screen. Second, the prediction assumes the aircraft holds its current heading, speed, and climb rate, because ADS-B carries no flight plan. An aircraft that turns cancels its transit. SpotFlight withdraws the prediction automatically when that happens, but nothing can foresee the turn.

Transit predictions can be turned off in Settings.

What do the coloured circles mean?

Green — above your horizon, so it is in the sky in front of you and you have a chance of seeing it. Orange — below your horizon: the direction and distance are correct, but the curve of the Earth is between you and the aircraft. Red — the aircraft is squawking an emergency code.

Why does the alert say an aircraft will pass close, and then nothing happens?

Because it turned, slowed, or started its descent. Every close-pass and transit prediction assumes the aircraft keeps doing what it is doing right now, which is the only assumption the data supports. SpotFlight recomputes every second and withdraws an alert as soon as the prediction stops holding — but it was still showing while it was true.

You can change the distance that counts as "close" (3–50 km, default 15) and how far ahead you are warned (30 seconds to 5 minutes, default 90 seconds) in Settings.

Alerts deliberately ignore passes that happen below one degree of elevation. Near a large airport, aircraft on approach otherwise generate constant alerts for landings ten kilometres away — technically a close pass, but not something you would look up for.

I searched a flight number and got nothing, or the wrong aircraft.

Two real limitations, both of which SpotFlight warns you about before you search.

Some airlines use callsigns unrelated to the ticket number. Ryanair, easyJet, Transavia, Wizz Air, and Jet2 assign dynamic alphanumeric callsigns — real examples: EZY46AB, RYR70LT, TVF715E. There is no way to derive those from a flight number. Search by aircraft registration instead (for example G-EZBI), which always works.

One airline code can map to several. easyJet flies as both EZY and EJU, so SpotFlight tries each in turn.

Also: search only finds aircraft the network can currently see. A flight that has not taken off, has landed, or is over an ocean will not be found. When a flight is found on the far side of the continent, SpotFlight still shows you its bearing and distance — it just tells you honestly that it is below your horizon.

Why do the numbers on screen keep changing slightly?

Because every position shown is extrapolated, not measured. A position from the network arrives with an age already attached, and more time passes before it reaches your screen. SpotFlight corrects for both delays, moving the aircraft forward along its track — and each time a fresh position arrives, the estimate is replaced by something better.

Past 20 seconds of age, SpotFlight says so on the label, along with how far the aircraft has travelled since the last real fix. Past 120 seconds it drops the aircraft entirely rather than showing you a fiction.

What units does SpotFlight use?

Distances in kilometres, altitude in feet and flight levels, speed in knots — the aviation convention. There is no imperial (miles) option yet. If you want one, say so.

Does it work in landscape? On iPad?

Portrait only, for now. The app runs on iPad in iPhone compatibility mode, but it is designed and tested for iPhone.

Do I need to pay again, or subscribe?

No subscription, and nothing to buy. The first 24 hours after you install the app are completely open — no video, no prompt, nothing asked. After that, the augmented-reality view and Sun and Moon transit prediction are unlocked for another 24 hours by watching a short video, which you start yourself. The map, the list, the search and the passage alerts are free and always available. No ad is ever shown on its own: the only one you will see is the one you choose to start.

It drains the battery.

It would. SpotFlight runs the camera, the motion sensors, GPS, and a network request every few seconds — the same load as any camera-based app. Close it when you are done; nothing runs in the background.

Data sources

Live aircraft positions contain information from adsb.lol, which is made available here under the Open Database License (ODbL).

Flight route information is provided by adsbdb.com. The flight route data is the work of David Taylor, Edinburgh and Jim Mason, Glasgow, and may not be copied, published, or incorporated into other databases without the explicit permission of David J Taylor, Edinburgh.

Aircraft position data is provided as is, with no warranty of accuracy, completeness, or availability. SpotFlight is for observation and enjoyment, and must not be used for navigation or any operational purpose.

Contact

Questions, bug reports, and feature requests are welcome — a real person reads them.

Email: mourad.toumi@icloud.com

Please include your iPhone model, your iOS version, the SpotFlight version (shown in Settings), and what you were doing at the time. For a wrong position, the callsign and roughly where you were standing helps a lot.

Typical reply time: a few days.