  We investigate the motion of an impurity particle injected with finite
velocity into an interacting one-dimensional quantum gas. Using large-scale
numerical simulations based on matrix product states, we observe and
quantitatively analyze long-lived oscillations of the impurity momentum around
a non-zero saturation value, called quantum flutter. We show that the quantum
flutter frequency is equal to the energy difference between two branches of
collective excitations of the model. We propose an explanation of the finite
saturation momentum of the impurity based on the properties of the edge of the
excitation spectrum. Our results indicate that quantum flutter exists away from
integrability, and provide parameter regions in which it could be observed in
experiments with ultracold atoms using currently available technology.
