Aircraft heard on 1090 MHz from the car.
Most aircraft broadcast their identity, position, and altitude on 1090 MHz (ADS-B). It's the same signal that sites like FlightAware collect, and the car's radio can hear it from the ground. On drives when the receiver is tuned to 1090 MHz instead of the tire-sensor bands, it logs which aircraft it heard and how high they were. Transponder broadcasts are public by design, so there's nothing to anonymize here.
Altitude of every aircraft heard. Airliners cruise around 30,000 to 40,000 ft, and the low end should be traffic in and out of Easterwood (CLL) and smaller fields nearby.
The most common airline codes among the callsigns heard (AAL is American, SWA Southwest, UAL United, DAL Delta, ENY and SKW regional). Private tail numbers are left out.