We develop a set-cover based integer-programming approach to an optimal safety-landing-site location arising in the design of urban air-transportation networks. We link our minimum-weight set-cover problems to efficiently-solvable cases of minimum-weight set covering that have been studied. We were able to solve large random instances to optimality using our modeling approach. We carried out strong fixing, a technique that generalizes reduced-cost fixing, and which we found to be very effective in reducing the size of our integer-programming instances.