On 7 July 2008, a Mc Donnell Douglas MD81 being operated on a US domestic ad hoc passenger charter by Air Midwest had just taken off from Chicago Midway Airport in day visual flight conditions when increasing pitch could initially not be controlled. As pitch was approaching 30 degrees nose up, flight crew control column and stabilser pitch trim inputs resulted in control being regained but with œhigher than normal pitch control pressure required to control the aircraft thereafter. Since this condition could not be resolved by flight crew action using available drills or after consultation with the operator™s ground maintenance staff, an en route diversion to St Louis MO was initiated and completed uneventfully.