The Croatian military police has launched a corruption probe in the July 2013 purchase of 12 Mikoyan MiG-21 fighter jets after they found five of the aircraft actually belonged to Yemen Air Force. Five of the aircraft purchased were quickly removed from service due to technical problems. With half of the order was too defective to function, the military police have started probing for corruption in the deal with Ukrainian Ukrspecexport, Sputnik reported Wednesday. All the 12 aircraft were delivered in July 2015. The investigation so far has revealed that the jets were fitted with outdated parts from Bulgaria, Algeria, and the former Soviet Union. These parts do not meet the technical requirements laid out in the contract signed by Ukrspecexport. Officials also found that five of the fighters were used, and, in fact, are currently property of the Yemen Air Force. As investigations continue, the Croatian government is shopping for additional aircraft to replace its aging fleet. At the top of the list are Lockheed Martin’s F-16 and Saab’s JAS-39. The government is also considering South Korea’s T-50, Israel’s Kfir, and the French Mirage.