This paper presents different mono camera-based aircraft sense and avoid methods considering linear and nonlinear own flight trajectories and steady and linear intruder trajectories. It introduces a new method which in certain circumstances is capable to estimate intruder absolute position and velocity. Its relation to a previously published method is formulated and its reduced version considering steady intruders is also shown. The limitations and advantages of all methods are evaluated mathematically and in Matlab tests and finally a list of their ideal capabilities and application guidelines are provided.