Since 2008, the workshops of Linz had several ES 64 U4 locomotives in stock, making it possible for Siemens to react quickly on customers with small orders. We consider #21314 being the first one built according to this strategy. Up to numbr #21320 this worked all fine, but then the economical crisis set in and several machines were completed, made thier maiden run, but had to be stored, waiting for better times. The following six units completed their maiden run in March and April 2009 (works numbers #21321, #21322, #21323, #21604, #21605, #21606 as far as we know) with a temporary service number (always 1216 999) and in their base coating. They were then stored in Linz.
During 2009 and 2010 another six locomotives were assembled in Linz without having a direct customer yet. All these units were sold gradually in 2010 and 2011 to operators, such as RTS, WLC and CargoServ from Austria and InRail and FUC from Italy.
In 2011 Siemens built yet another batch of U4-locomotives in Munich, starting with the white 183 712 and 713.