Air Berlin was a German low-cost and leisure carrier that grew to become the second-largest airline in Germany, after Lufthansa. Founded in 1978 and headquartered in Berlin, it operated an extensive network of routes across Europe, North America, and holiday destinations worldwide. The airline faced persistent financial difficulties throughout the 2010s, accumulating significant debt despite efforts to restructure. Etihad Airways held a major stake in Air Berlin and provided financial support for several years, but ultimately withdrew its backing in 2017. Air Berlin filed for insolvency in August 2017 and ceased all flight operations on October 27, 2017. Parts of its operations and assets were acquired by Lufthansa, easyJet, and other carriers following the collapse.