This document provides guidance for national competent authorities (NCAs) to consider when granting exemptions under Art. 71(1) of Regulation (EU) 2018/1139 (hereinafter, the Basic Regulation) allowing the installation of equipment on aircraft for the transport of Highly Infectious Desease (HID) patients. Such equipment, hereafter called patient isolation device (PID), shall reduce the risk of contamination of crews and medical teams.