This dataset is the associated input for the software, traffic-density-database. It is intended to process observed aircraft traffic information into unmitigated collision rates given user specified geographic regions or aircraft tracks. The user may also specify the time of day, month of year, and day of week to be evaluated. Unmitigated collision rates are useful for aircraft safety assessments, and may be combined with the efficacy of mitigations—e.g., air traffic control, detect and avoid, see and avoid—in order to estimate the total operation safety. The input data included with this release has the following attributes. See the README in the Data directory for more detail on the contents of each data file. The data span 8727 observed hours, from 4 November 2018 to 3 November 2019. Note that there are periods where there are no radar data available, so the data span does not correspond directly to the full date range extent. There are over 31.65 million flight hours observed (includes both discrete-code and 1200-code aircraft). The vertical spatial (height) discretization corresponds to standard altitude feature thresholds in the national airspace: 100 feet Above Ground Level (AGL): Cutoff to exclude on-ground traffic 500 feet AGL: nominal lower manned aircraft operating altitude 1200 feet AGL: typical lower altitude for Class E airspace 3000 feet AGL: approximate upper bound for Class D airspace 5000 feet AGL: approximate upper bound for Class C airspace 10,000 feet Mean Sea Level (MSL): typical Class B upper bound, and lower threshold for transponder requirements 18,000 feet MSL: lower bound for Class A Airspace 29,000 feet MSL: Reduced Vertical Separation Minimum (RVSM) lower altitude bound 41,100 feet MLS: RVSM upper altitude bound 60,100 feet MSL: upper bound for Class A Airspace The temporal discretization is 3 hours. The latitude range is 22.83°N to 50.00°N. The longitude range is 127.00°W to 64.83°W. (Note: MATLAB indicates W longitude using negative numbers, e.g., 127.00°W is -127.00.) Two tables with different horizontal spatial discretization are provided: one for all altitudes, where the discretization is 1/6 of a degree in latitude and longitude (corresponding to approximately 10 NM); and one for altitudes below 5000 feet, where the discretization is 1/24 of a degree (approximately 2.5 NM). The table containing all altitudes is the default.