A Frontier Airlines Airbus A320-200, registration N203FR performing flight F9-722 from Denver,CO to Washington National,DC (USA), was enroute at FL350 about 80nm northwest of Kansas City,MO (USA) when the crew reported a cracked windshield and decided to divert to Kansas City for a safe landing about 30 minutes later. A replacement A320-200 registration N236FR reached Washington with a delay of 3:20 hours.