The aim of the work was to identify the key factors involved in the use of alternate spectrum in various bands for a future integrated CNS data link. The study focused on systems and spectral bands that can deliver VDL-or-higher data rates in a two-way communication setting (including air-ground, ground-air, and air-air modes of operation), with multiple platforms (aircraft) operating in the same local environment. We begin with a review of the initial task list, and the final task list. The final task list contained a focus upon spectral availability and related systems that could be affected by the deployment of a new aviation data link (ADL) system. Most of this addresses the lower few layers of the communications protocol stack. A brief review of current related efforts in the aeronautical community is then provided, in which we describe several systems and programs of interest. Participation in some of these efforts is recommended. We also delineate several of the advantages and disadvantages of these system/efforts, in view of anticipated requirements of a new ADL. Desired attributes of a new ADL system are then discussed, and a connection with existing systems is made. The need to consider a wider set of alternative systems and technologies is described, and the beneficial aspects of a particular transmission technique- spread spectrum-are discussed. We then discuss in more detail several potential spectral regions, in terms of propagation conditions, available technology, spectrum availability, and waveform selection. Some comments on the need for standardization are also provided. We note that none of the existing systems described will likely meet the full range of desired features of a new ADL, but that several systems and spectral regions offer promise in terms of one or more characteristics. A system design and analysis approach is then provided. In this, we again focus on the lower few layers of the protocol stack, and aim to capture the main features ...