Topics

Large freighters, military transports and other aircraft types that seldom appear in these Michigan records, with the data behind each match.

The first time an aircraft type, or an address block assigned to a country, appears in these Michigan records, with the dates behind the claim.

Douglas DC-3s, wartime trainers and other aircraft at least 80 years old by their database records, recorded in flight.

Aircraft listed in Plane Alert DB, a community list of aircraft that spotters follow, with the list category and the limits of what an entry shows.

Balloons broadcasting ADS-B from 50,000 ft and higher while moving slowly over the ground, and how the site tells them apart from data glitches.

Aircraft holding close, matching tracks at altitude: formation-like pairs found in broadcast positions, with their spacing and duration.

Aircraft flying long, evenly spaced parallel lines, the pattern used for aerial photography, mapping and other survey work.

Three or more aircraft holding at the same time, stacked at different altitudes while they wait for a clearance.

Helicopters that stayed nearly stationary in the air, checked against movement before and after so parked aircraft are not counted.

Gliders climbing in tight circles inside rising air, found from their tracks, climb rates and speeds.

Aircraft that circled down through 1,500 ft or more, measured from saved positions, with what a flight shape can and cannot tell you.

Aircraft that descended at 4,500 ft per minute or more, measured from their reported vertical rates and altitudes, with what a fast descent can and cannot show.

Aircraft that flew unusually fast over the ground or unusually high, from direct ADS-B reports, with tailwinds and altitude references explained.

Aircraft transmitting the general emergency, radio failure, hijack or other special transponder codes, and why a code alone does not confirm an emergency.

Resolution advisories from aircraft collision-avoidance systems, decoded from transponder broadcasts, with the response and spacing the data shows.

Readings that cannot be right, such as thousand-knot spikes, impossible altitudes and identity mismatches, shown with the neighboring reports.

Groups of aircraft that lost navigation integrity in their ADS-B data at about the same time, and what those integrity fields can and cannot show.