Boeing has delayed the first test flight of the 787 Dreamliner by about three months to almost July and said it won’t start deliveries until early 2009, the second setback for the planemaker’s most successful new jetliner based on orders.

The Dreamliner was already six months behind schedule and continues to be hurt by incomplete parts being delivered to Chicago-based Boeing, which has racked up 817 orders valued at more than $120 billion at list prices. There will be “no material impact” on the earnings forecast for 2008, the world’s second-biggest commercial planemaker said in a statement today.

“This is difficult call to make, but one that is right for the program,” Scott Carson, Boeing’s chief executive officer commercial aircraft, said on a conference call. “We’re deeply disappointed by what this delay means for our customers.”