This thesis examines joint radar and communications (RadCom) techniques for airborne systems. This is motivated by a convergence of radar (remote sensing) and wireless communications technologies, which have historically been separate in terms of hardware, deployment and processing techniques. A particular waveform that prompts interest is the orthogonal frequency-division multiplexing (OFDM) waveform, which is prevalent in modern wireless communications networks. This thesis reviews the literature and remarks on my contributions to remote sensing through exploiting OFDM signals using Fourier-based techniques; use of constant modulus OFDM signals in a dual-function context; introduction of matrix pencil-based solutions to the target parameter estimation problem; and aspects affecting the feasibility of OFDM-based RadCom design. The thesis is concerned with airborne systems, which motivates examination of techniques suited to the 3D geometry of a base-station observing or communicating with a target or user at a different altitude. Extension of established techniques to comply with this is presented alongside parametrisation of systems to comply with fifth generation (5G) telecommunications standards, and observation of extended targets modelled as collections of points. OFDM signals typically have a high peak-to-average-power ratio (PAPR), which hampers the ability to operate power amplifiers efficiently: an examination is undertaken of the construction and performance of constant modulus OFDM waveforms when used for remote sensing. Then, matrix pencil based techniques are examined as an alternative parameter estimation technique for performing high-precision, limited snapshot estimations on one or more targets. Various aspects of the system design are explored, such as power and performance, helping to assess the feasibility of developing deployable systems.