Boeing has delayed the first delivery of its 747-8 Freighter until the middle of 2011. The company is taking to support the new schedule, including adding a fifth airplane to the flight-test fleet. The new delivery schedule follows the detection of a low-frequency vibration in certain flight conditions and an underperforming aileron actuator. While neither issue requires structural changes to the airplane, they have led to disruptions to certification testing, which the programme was unable to offset within the prior schedule, Boeing said.