United Airlines officials say no one was injured when the wing tips of two planes touched on the ground at O'Hare International Airport.  United spokeswoman Megan says no one was injued in the Wednesday afternoon incident.  She says the Boeing 767s had pushed back from adjacent gates when one plane moved forward and the wing tips touched.  She says both planes were damaged and immediately returned to their gates.  Passengers on the planes moved to new flights.  United is investigating the extent of damage to the planes.