Airspace monitoring for event security is the layer between "we filed a TFR" and "what's actually flying over the crowd right now." SignalGuard's airspace signal pulls live ADS-B state vectors from OpenSky Network and surfaces helicopters loitering over the venue, low-altitude overflights, and emergency squawks — the same picture a police air-traffic liaison would brief in person, available continuously to your security ops dashboard.
What this signal monitors
The Airspace signal reports every ADS-B-broadcasting aircraft within a bounding box around the venue (default 7 km), including helicopters (police, news, EMS, media), loitering or circling aircraft, low-altitude overflights, and emergency-squawk transponder codes (7500 hijack, 7600 nordo radio failure, 7700 general emergency). Each aircraft includes its callsign, registration, aircraft type and operator, altitude (ft), ground speed (kt), vertical rate, squawk code, and heading.
Data sources
SignalGuard's airspaceClient.js queries the community ADS-B feeds airplanes.live (primary) and adsb.lol (fallback) for aircraft within a radius of the venue — both are free, key-less, and built for programmatic access. (We previously used the OpenSky Network, but its API blocks datacenter egress IPs, so it was unreachable from our hosting.) Aircraft identity — registration, type, model, operator — comes inline with each record. Important coverage caveat: ADS-B covers aircraft broadcasting a transponder — commercial fixed-wing, general aviation, helicopters, and larger commercial drones. Consumer drones (DJI, etc.) broadcast FAA Remote ID rather than ADS-B, so they do NOT appear in this signal. For drone-specific monitoring, pair with FAA NOTAMs for pre-planned UAS NOTAMs and BYOK a Remote ID provider on /integrations.
How SignalGuard scores severity
Per-aircraft classification: any emergency squawk (7500/7600/7700) is critical regardless of context. Low-overhead helicopters (under 600 m baro altitude AND helicopter-like profile) are high. Loitering aircraft (under 2500 m, under 70 m/s ground speed, near-zero vertical rate — the orbit pattern media/police helicopters fly) are high. Generic helicopter-like profiles (under 1500 m, under 80 m/s) are medium. Everything else is low. The overall level bumps to medium at 8+ aircraft total and high at 3+ helicopters — concentrated airspace activity around a venue is itself anomalous even when no single aircraft is dangerous. OpenSky's category field is optional and frequently absent, so SignalGuard infers helicopter-like behavior from altitude and speed signatures rather than asserted aircraft type.
Use cases for event security
- Hold doors when this signal is HIGH because press helicopters indicate an incident-in-progress. Three or more loitering helicopters above the venue area, especially with news-network ADS-B callsigns, mean something is happening on the ground that you may not have heard about yet. Cross-check scanner feeds before doors open.
- VIP arrival airspace clearance verification. When a TFR is published for the venue (see TFR monitoring) and an arrival is imminent, the airspace card should show only authorized aircraft inside the inner ring. Any unauthorized loitering targets a real-time call to ATC.
- Emergency squawk awareness. A 7700 squawk on a flight passing the venue at altitude is almost certainly unrelated to your event — but it tells your team to expect emergency vehicle response on the access roads to a possible diversion airport, which affects ingress and egress.
Pairs well with
- TFR monitoring — the published restriction vs. the actual traffic.
- FAA NOTAM monitoring — drone and special-use airspace notices.
- Police scanner feeds — what the press helicopters are circling.
Premium upgrade path
For consumer drone detection (FAA Remote ID), BYOK Aerial Armor or Dedrone on the Integrations page. For higher-cadence commercial flight tracking, Flightradar24's commercial API, FlightAware AeroAPI, and ADS-B Exchange Enterprise supersede the OpenSky anonymous tier. OpenSky also offers a paid tier with higher rate limits and the same data shape — SignalGuard supports both transparently.
Frequently asked questions
Does SignalGuard monitor drones over events? ADS-B-broadcasting commercial drones appear in the airspace signal. Consumer drones (DJI, Autel) broadcast FAA Remote ID, not ADS-B — for those, BYOK a Remote ID provider like Aerial Armor or Dedrone.
What does an emergency squawk code mean? Three reserved transponder codes signal in-flight emergencies: 7500 (hijack), 7600 (radio failure), 7700 (general emergency). Any of these escalates the signal to critical.
Why is OpenSky sometimes unreachable from my dashboard? OpenSky's anonymous tier blocks certain cloud egress IP ranges at the network edge. SignalGuard serves recent cached results when this happens and surfaces a "stale" indicator. Upgrade to OpenSky paid or BYOK Flightradar24 to remove this limit.
Can I see what helicopter is circling the venue? Yes — the signal returns the ADS-B callsign and origin country for each aircraft. Many news helicopters have publicly identifiable callsigns (e.g., N911MM patterns) that map to specific stations.
Does the airspace signal cover international venues? Yes — OpenSky has global ADS-B receiver coverage with strongest density in North America and Europe. See the SignalGuard docs hub.
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