In this paper, the feasibility of multiple-input multiple-output (MIMO) systems in aircraft is examined for the specific application of seatback entertainment, using an approach built around a site-specific capacity analysis methodology. The average capacity is evaluated as a function of the seat location, using the proposed methodology that relies on inputs from measurement results or ray-tracing simulations. The extension of the methodology to optimize the access point and client antenna placement locations and array configurations is also described in the paper. While the specific results are for the deployment of MIMO communication in aircraft for seatback entertainment, the same methodology can be applied to other deployment scenarios as well.