The Performance Review Body (PRB) supports the European Commission in implementing the Single European Sky's (SES) performance and charging scheme. The 2019 PRB Annual Monitoring Report offers an in-depth assessment of the performance of monopolistic air navigation service providers (ANSPs) subject to Union law. As 2019 was the final year of the second reference period (RP2) that had started in 2015, this year's edition also includes an assessment of the entire RP2.