An apparatus, method and computer program is described comprising: determining a set of candidate radio resources for transmitting data from a first communication node of a non-terrestrial network to a second communication node of the non-terrestrial network over a direct radio link; identifying one or more of the candidate radio resources as conflicting radio resources that conflict with at least one scheduled radio transmission in the non-terrestrial network based, at least in part, on a propagation delay associated with the at least one scheduled radio transmission and/or a propagation delay associated with the radio transmission by the first communication node; generating a subset of candidate radio resources by excluding the identified one or more conflicting radio resources from the set of candidate radio resources; and selecting a radio resource from the subset of candidate radio resources for transmitting the data over the direct radio link.