The United States recently stepped in and blocked an effort by Uzbekistan to buy twelve South Korean T-50 jet trainers. These aircraft go for $34 million each (including training, spare parts, and some tech support). The United States was able to block the T-50 sale because the aircraft uses American jet engines and a lot of American electronics. All this stuff requires American permission before it can be exported as part of an aircraft. Normally this is not a problem. Indonesia, Iraq, the Philippines and Thailand have also bought the T-50s with no problem. None of those countries pose any technology theft risks.
Uzbekistan however has close military, political and economic ties to Russia and China. Similar concerns also led to the recent refusal of the United States to transfer several key military technologies so South Korea could build its locally designed KFX jet fighter. The refusal was because of American security concerns. This is more of a problem in Asia as East Asian nations (like Japan several times in the past) have proved vulnerable to China spies seeking to obtain key military technologies. Not just the specifications but the more difficult to obtain details of actually manufacturing such tech. Most of the technologies the U.S. will not give South Korea access to are only available from a few sources, or only the United States.
The single engine, two seat T-50 can also be used for combat with about $10 million worth of additions and upgrades. The South Korean designed and manufactured T-50 jet trainer was developed after more than a decade of effort at a cost of over two billion dollars. The first test flight of the T-50 took place in 2002. The 13 ton aircraft is actually a light fighter and can fly at supersonic speeds. With some added equipment (radars and fire control) the T-50 becomes the TA-50, a combat aircraft. This version carries a 20mm auto-cannon and up to 4.5 tons of smart bombs and missiles plus electronics to make all that work. The T-50 can stay in the air about four hours per sortie and has a service life of 8,000 flight hours.