Boeing said today that a fire onboard one of its test 787 Dreamliners has caused its test program to be delayed. Seen here, the first 787 takes off on its initial flight on Dec. 15, 2009.

Boeing today said that it has decided to halt tests of its much-anticipated but beleaguered 787 Dreamliner after an onboard fire during an evaluation flight.

The fire took place aboard ZA002, the second test 787, as it approached Laredo, Texas, Boeing said. The plane lost primary electric power but was able to land safely due to deployment of its backup systems, including its Ram Air Turbine. Boeing is investigating the electrical fire and said that early indications are that a power control panel in the plane's aft electronics bay must be replaced. Other repairs may also be required. An investigation of the incident is expected to take several days.

Because it is not known what caused the fire, Boeing also suggested that the entire 787 Dreamliner program could be on hold, though it will continue to conduct ground test operations in the interim. "We cannot determine the impact of this event on the overall program schedule until we have worked our way through the [investigation] data," the company said in a release this afternoon.

News of the fire and the test program hiatus hit Boeing hard on Wall Street. The company's shares were down 3.15 percent, or $2.18 today.

Of course, this is just the latest in a long string of delays that have stung the promising new airplane. While Boeing has built up tremendous buzz around the plane, which is expected to offer airlines big improvements in fuel efficiency, flight range, and passenger comfort, it has struggled to keep the program on track.

The most recent setback, in August, came after Boeing announced that it was re-assessing the availability of an engine it needed for last stages of its flight tests. But there have also been a string of other problems including a machinists strike, supplier shortages, and an issue with the joint between the fuselage and the wing. The latter problem resulted in the 787's first flight, which finally took place last December, being delayed for two years.

Until today, Boeing had said it would be delivering its first Dreamliner in the first quarter of 2011. Clearly, that schedule is now threatened.