This much is known about Kennedy's last flight:

Kennedy, Carolyn Bessette Kennedy and her sister Lauren Bessette arrived at Essex County Airport near Fairfield, N.J., where Kennedy kept his single-engine Piper Saratoga II plane, at dusk on Friday.

Kyle Bailey, the New Jersey pilot who is believed to be the last person who saw the trio, was also planning a flight to Martha's Vineyard, but he canceled his plans because of poor visibility. "The weather was very marginal, four to five miles visibility, extremely hazy," Bailey told the Washington Post. "Over open water, you have reduced visibility anyway. With the haze, in the dark, you lose sight of the horizon. You don't have landmarks."

After loading their baggage and taxiing, the Kennedys' plane departed at 8:38 p.m. from runway 22. The plane made a 180-degree turn toward the northeast. According to radar data, the plane then climbed to 5,600 feet and continued easterly along the coast until it came to Westerly, R.I., at 9:26 p.m. After passing Westerly, Kennedy's plane began its descent toward Martha's Vineyard.

At 9:40, the plane was about 17 miles from the airport at Martha's Vineyard, and had descended to 2,200 feet, maintaining that altitude for 20 seconds. The last blip on the radar screens at Provincetown, Mass., and Cape Cod approach controls, where the plane was tracked, came 14 seconds later, at an altitude of 1,100 feet. In just 14 seconds, the plane dropped 1,100 feet, compared to the 400-500 feet per minute norm at that stage of landing. Then complete radar silence. No signs of distress. Eerie silence.

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