The number of individuals traveling by airplanes is increasing every year. Patients with congenital heart disease and shunts, exposure to high altitude during a flight is important since it causes pulmonary vaso- constriction leading to an increase in right-to-left shunting and a decrease in arterial oxygen saturation. Patients with cyanotic congenital heart disease and Eisenmenger syndrome should be evaluated before the flight, and necessary precautions should be taken.