Air Serbia has arranged a short-term wet-lease of one of its Boeing 737 aircraft, operated under the Aviolet charter brand, to Etihad Airways partner Air Berlin. The 29-year-old jet, registered YU-ANJ, began operating flights for Germany’s second largest airline this morning between Cologne, Berlin and Stuttgart. The cash-strapped Air Berlin is to slash its operating fleet and allocate forty aircraft to the rival Lufthansa Group, in a significant restructuring effort that will cost more than 10% of the airline's workforce. Air Berlin has required repeated bailouts from shareholder Etihad. This summer, Air Serbia leased the same B737 to Montenegro Airlines for several days.