Unidentified aircraft flying through South Dakots air space.These craft have been observed by us since December 2011. The contrails they leave attracted our attention. They are lond and WIDE unlike those left by commercial airliners. Most flights originate from the west and track east and some from the northwest and track southeast. For help in identifying these craft I have contacted TV stations in Sioux Falls and even NORAD but no one has responded. So, perhaps you folks can help. Are they a new generation reconnaissance aircraft?