BACKGROUND: During commercial air travel passengers are exposed to a low ambient cabin pressure, comparable to altitudes of 5000 to 8000 ft (1524 to 2438 m). In healthy passengers this causes a fall in partial pressure of oxygen, which results in relative hypoxemia, usually without symptoms. Patients with congenital heart or lung disease may experience more severe hypoxemia during air travel. This systematic review provides an overview of the current literature focusing on whether it is safe for patients with congenital heart or lung disease to fly.METHODS: The Pubmed database was searched and all studies carried out at an (simulated) altitude of 5000–8000 ft (1524–2438 m) for a short time period (several hours) and related to patients with congenital heart or lung disease were reviewed.RESULTS: Included were 11 studies. These studies examined patients with cystic fibrosis, neonatal (chronic) lung disease and congenital (a)cyanotic heart disease during a hypoxic challenge test, in a hypobaric chamber, during commercial air travel, or in the mountains. Peripheral/arterial saturation, blood gases, lung function, and/or the occurrence of symptoms were listed.DISCUSSION: Based on the current literature, it can be concluded that air travel is safe for most patients. However, those at risk of hypoxia can benefit from supplemental in-flight oxygen. Therefore, patients with congenital heart and lung disease should be evaluated carefully prior to air travel to select the patients at risk for hypoxia using the current studies and guidelines.Spoorenberg ME, van den Oord MHAH, Meeuwsen T, Takken T. Fitnesss to fly testing in patients with congenital heart and lung disease. Aerosp Med Hum Perform. 2016; 87(1):54–60.