By Wayne Heilman wayneh@gazette.com -The U.S. Department of Transportation confirmed Monday it is investigating an incident Friday in which passengers on a United Express flight diverted to the Colorado Springs Airport spent nearly six hours on the tarmac before they were allowed to leave the aircraft. The Associated Press reported Saturday that United Express Flight 4934, operated by Republic Airlines, was one of eight flights diverted Friday from Denver International Airport to Colorado Springs because of weather.