General aviation and small unmanned aircraft systems are less redundant, may be less thoroughly tested, and are flown at lower cruise altitudes than commercial aviation counterparts. These factors result in a higher probability of a forced or emergency landing scenario. Currently, general aviation relies on the pilot to select a landing site and plan a trajectory, even though workload in an emergency is typically high, and decisions must be made rapidly. Although sensors can provide local real-time information, awareness of more distant or occluded regions requires database and/or offboard data sources. This paper considers different data sources and how to process these data to inform an emergency landing planner regarding risks posed to property, people on the ground, and the aircraft itself. Detailed terrain data are used for selection of candidate emergency landing sites. Mobile phone activity is evaluated as a means of real-time occupancy estimation. Occupancy estimates are combined with population census data to estimate emergency landing risk to people on the ground. Openly available databases are identified and mined as part of an emergency landing planning case study. = total number of country codes n g = total number of grid cells n t = total number of time intervals R a = risk based on landing area R h = risk to people on ground R ls = overall landing site risk R p = risk to property on ground R v = risk to vehicle t = time, min t 10 m = starting time of 10 min time interval, min W h , W p , W v , W a = weights associated with landing site risks w = A transition cost weight Θ = median of maximum aggregated SMS and call activity during a day, for a day of the week λ census = occupancy from census datâ λ census = normalized occupancy from census data λ rt = real-time occupancy estimation λ 0 = A fixed transition cost element Φ = median of aggregated SMS and call activity for each grid cell, day of the week and time interval of the day Φ grid = sum of Φ for all grid cellŝ Φ = normalized Φ ϕ = aggregated SMS and call activitŷ ϕ = normalized ϕ ϕ 1 = activity in terms of SMS-in ϕ 2 = activity in terms of SMS-out ϕ 3 = activity in terms of call-in ϕ 4 = activity in terms of call-out ϕ 5 = activity in terms of internet ϕ i = modified activity feature for heat map plot