The wreckage of John F. Kennedy Jr.'s plane showed no signs of in-flight breakup or fire, and the engine appeared to have been working when the aircraft plunged into the ocean, a federal safety panel said Friday. The National Transportation Safety Board in Washington, D.C., releasing its first update in a week on its investigation of the July 16 crash that killed Kennedy, his wife Carolyn Bessette Kennedy and her sister Lauren Bessette, also said that 75% of the plane was recovered from the waters off Martha's Vineyard, Mass., including a primitive recording device. That instrument, however, was destroyed by the impact.