The integration of Unmanned Aircraft Systems (UAS) into the National Airspace System (NAS) requires that UAS meet or exceed the safety requirements established for conventional aircraft, and for the UAS pilots to interact with air traffic controllers (ATCos) in an acceptable manner.UAS have several characteristics that differentiate them from conventional aircraft, including the possibility of greater latencies associated with remote pilot communication and command execution. The goal of the present study was to determine how adding delays to UAS pilot communications and command executions affect ATCos' interactions with UAS and conventional aircraft. Six previously certified radar controllers and two currently certified radar controllers were recruited as participants to manage traffic in a simulated sector with conventional traffic and one UAS flying in it. The UAS pilot verbal communication and execution latencies were varied in separate scenarios to include an additional delay that was either short (1.5 s) or long (5 s), and constant or variable within each scenario. We measured both UAS and conventional pilots' verbal communication and execution initiation latencies, and obtained ATCos' acceptability ratings for the different delay conditions. Also examined were the number of communication step-ons created by the additional communication delays implemented in the UAS control station, as well as other measures of the ATCo-pilot interactions. We found ATCos rated UAS pilot verbal communication latencies to be acceptable when the latencies were short rather than long and that acceptability ratings often reflect broader features of the sectors being managed. Implications of these findings for UAS integration in the NAS and limitations of the present study are discussed.