Why flight trackers miss aircraft

Why a plane can be missing

A plane can be plainly visible above you and absent from a flight tracker. A public map needs usable aircraft data, a route for that data to reach the service, and permission to display it. A break anywhere in that chain leaves a gap. The same gap can have different causes, so a missing icon does not tell you whether the aircraft stopped broadcasting, left reception range or is simply outside that service's coverage.

ADS-B is one common source. An aircraft broadcasts information from its own systems, including its identity and position. EUROCONTROL describes this as automatic and dependent on the systems aboard the aircraft [1]. Our ADS-B introduction explains the receiving chain. This article is about reading the resulting map when that chain is incomplete.

Receiver coverage is local

A receiver hears the aircraft around it. Hills, buildings, aerial placement and the height of the aircraft can change what it receives. A busy map over a major airport does not establish equally good coverage in a nearby valley. Your own receiver may hear a plane that a shared network misses, or the network may have receivers that hear traffic your aerial cannot.

Low aircraft are a particularly useful test of local reception. If high airliners appear regularly but nearby helicopters or aircraft on approach vanish, inspect your aerial's view of the horizon before assuming the decoder has failed. Compare similar flights at similar heights over several days. A single missing flight cannot separate an obstruction from a temporary outage. The antenna placement guide and reception checklist give a practical way to investigate.

Why two flight trackers show different aircraft

Each tracker has its own sources and display rules. Flightradar24 describes a combination of ground and satellite ADS-B, multilateration, radar in some regions and other inputs [2]. Access to one source does not mean every public tracker receives it. Different refresh intervals can also make two maps disagree for a short time.

To compare services fairly, pick the same registration or aircraft identifier, place and time. Then look for the timestamp and the stated source of the position. Do not compare a current icon on one map with a replay on another. If one service has only a flight schedule, that schedule is useful context but does not establish where the aircraft is now. An expected arrival and a received position answer different questions.

ADS-B positions and multilateration

An aircraft's identification message is not always a usable position report. Some aircraft can appear in a receiver's list without having coordinates that a map can plot. That is why seeing a callsign in a decoder does not guarantee an icon on a public map.

Multilateration, usually called MLAT, is another way a network can calculate a position. It uses reception timing from multiple receivers. Flightradar24 explains that it uses this for aircraft with older transponders that send less data [2]. Receiver geometry and usable timing matter, so hearing an aircraft at one station does not establish that MLAT is available for it. The MLAT guide explains what the participating receivers must provide. An ADS-B position and an MLAT position should retain their source labels.

What to check in the UK and Europe

Choose the receiving equipment for the signal you want to hear. EUROCONTROL's Mode S and ADS-B compendium identifies 1090 MHz Extended Squitter as the ADS-B data link used in Europe [3]. A description of a US receiving setup may include a separate UAT chain. Do not copy its hardware list without checking the frequency, aerial and decoder against your own goal.

Start with a local question. Can the receiver see aircraft on the approach you care about, or only airliners high overhead? Does its output include recent positions? Can you still read the local aircraft list if an external network is unavailable? Work through the first receiver guide, then compare the hardware options and installation paths. Check local requirements before installing outdoor equipment or sharing data. This guide does not establish legal permission for a particular installation.

Read the timestamp before the moving icon

A map can animate smoothly while its underlying observation is old. A moving icon is therefore not, by itself, proof of a newly received position. Read the age or last-observed time where the service supplies one, and distinguish the observation from any motion drawn between updates.

These are interpretation checks, not a promise that every tracker uses the same labels. If a service does not disclose the age or source, you have less information for judging the point. Avoid turning that uncertainty into a precise statement about the aircraft's current location.

Where Skylark works today

Skylark's live service is focused on Ireland, with its established Dublin picture. Reception outside that picture depends on available observations and contributors. The receiver network and Irish airport pages explain the places and data available to the product. A map without aircraft is not proof of an empty sky.

Skylark does not currently promise live coverage across the UK or continental Europe. This article explains flight tracking for readers in those places; it is not an announcement of a new regional service. If your local question is outside the collected area, use a service whose coverage includes it. You can still use Skylark's aircraft library and receiver field guide wherever you are.

In the supported Irish picture, identify the aircraft over your house or explore the rare aircraft observed over Ireland this week. Keep the observation date attached when sharing a sighting. A weekly record is historical evidence of an observation, not a claim that the same aircraft is overhead now.

A practical missing-flight checklist

1. Confirm that you are looking at a current view. Check the date if you arrived through a saved replay or shared link.
2. Use the registration or aircraft identifier when you can. A callsign can describe a flight and may be reused, so a familiar callsign alone is not proof of the same aircraft.
3. Look for the last observation time and whether the map labels the position as received, calculated or cached.
4. Check whether other nearby aircraft have recent updates. Several old observations can point to a service or data problem rather than a problem with one aircraft.
5. Check the service's stated coverage. An airport reference page, runway diagram or weather report does not establish live aircraft reception there.
6. If you run a receiver, compare its local decoded aircraft with the network view. The troubleshooting guide helps separate reception, decoding and feeding.

Record the time, identifier, place and what each source actually showed. That gives an operator something to investigate. Saying only that a plane was missing does not identify which part of the chain failed. You can report a Skylark problem through the contact page.

How a receiver can improve coverage

A receiver in a place with poor reception can add observations that a network otherwise lacks. It cannot promise complete coverage, and moving an aerial is not a substitute for checking that the feed works. First establish a working local decoder, then follow the chosen network's sharing instructions.

If you already operate a station in Ireland, read how to add Skylark beside your existing feeds. Keep your working setup and verify that the new feed has accepted data. The feeding networks guide separates receiving software from feeder software. The security and privacy guide covers what to review before exposing services or sharing station details.

For a UK or continental European station, consult the network's actual area support and terms before connecting. A successful installation command alone does not prove that the public map uses the station's data. Verify an accepted observation and its timestamp in the receiving service.