The Chinese J20 has changed the balance of power in their favor over the United States. Whether or not the J20 is a more capable aircraft than the F35 is irrelevant. The Chinese were not expected to field this aircraft for another 5-10 years. By doing so, it has put the United States on notice that it is committed to maintaining a modern fighting force. The US has been trying to field the F-35 to replace the aging legacy fighters such as the F-15, F-16 and F/A-18. The first flight of the F-35 occurred in 2006 and cost overruns now place the F-35 as the single most expensive weapon system ever and it still isn't fielded! The US military-industrial complex just is not nimble enough to rapidly field new technology and the speed of the Chinese system should be cause for concern. Getting into another arms race with China is something the US probably won't win.