Flight Register

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Airframes lists an aircraft only when a federal on-time record names it on two or more of your flights, so it is a floor rather than a total: nineteen international legs carry no tail number, and 22 recent legs await federal data that has not published yet. Type and build year come from the FAA registry, which reports the current holder of an N-number, so a very old entry may describe an aircraft that inherited the tail later. Retired means the registration has since been cancelled; the flight still happened.

Cities chains your legs into stays: you are in a place from the moment you land until the moment you next take off. Nights are counted as departure date minus arrival date, so a two-night trip touches three calendar days. Baltimore, National and Dulles are treated as one home node, since Annapolis drives to all three. Two cases are called out rather than silently averaged:

• Overland — you landed in one city and next departed from another within 250 miles, as when you flew into Rome and out of Venice. The span is credited to the arrival city.
• Passed through, drove home — you landed away from Baltimore and the next flight left from a home airport, so you finished the trip by road. Philadelphia after Venice, Kennedy after Rome. Those nights go to home, and the arrival airport is credited with a pass-through rather than a stay.
• Return flight not in the record — the next departure is more than 250 miles from where you landed, so the flight home is simply missing from the email. The nights are still credited to the city as the best available estimate, but they are an upper bound.
• Record gap — a span longer than 30 nights means a flight is missing rather than a month-long trip. Those are shown but excluded from every total.