Atmospheric jets are known to be an important source of inertia-gravity waves, yet remain poorly understood as such. Previous studies on the subject have concentrated on the generation mechanisms for the gravity waves, with the underlying assumption that the characteristics of the waves were imposed by the generation mechanism. In proceeding so, effects due to the propagation of the waves through a complex three-dimensional flow have been overlooked. Using numerical simulations of idealized baroclinic instability in a periodic channel, we show that propagation effects can determine several characteristics of the gravity waves emitted into the middle atmosphere from tropospheric jets. Specifically, the numerical simulations demonstrate that the propagation of inertia-gravity waves through horizontal deformation and vertical shear strongly influences the spatial organization of the waves and imposes the 3D orientation of their wave-vector.