We present the case of an otherwise asymptomatic patient with a rare congenital airway abnormality of the tracheobronchial tree, who developed a complete airway obstruction after being placed in the prone position. The tracheal bronchus, accessory bronchus arising from the trachea superior to its bifurcation at the carina, was identified by fiberoptic bronchoscopic examination. An endotracheal tube can migrate into a tracheal bronchus causing pulmonary atelectasis, hypoxia, or both.