Two Navy salvage ships sailed into the roiling Atlantic Ocean tonight, hoping to take advantage of a predicted one-day lull in the gale that has blocked recovery of two on-board recorders from the wreckage of EgyptAir Flight 990.

Rear Adm. W.G. Sutton of the Navy's Amphibious Group 2 said the USS Grapple and the ocean tug Mohawk would battle 15-foot seas through the night to be on site at dawn Friday. He said National Oceanic and Atmospheric Administration and Navy meteorologists had predicted that during daylight hours waves would fall below seven to eight feet--the maximum height that would allow for safe launching of a remote diving vessel. A third vessel, NOAA's Whiting, joined the flotilla.

The New York-to-Cairo flight crashed early Sunday morning about 60 miles off Nantucket, Mass., abruptly diving from 33,000 feet and killing all 217 people aboard.

A preliminary Air Force analysis of radar data indicated that the Boeing 767 dived from 33,000 feet to about 16,000 feet, reaching or exceeding the speed of sound. But it then inexplicably climbed back to 24,000 feet before beginning a final dive.

The plane apparently broke up at about 10,000 feet, sending numerous pieces drifting slowly down with the wind.

Several outside radar specialists today privately expressed skepticism about the analysis, asking whether it could be based on flawed data.

National Transportation Safety Board Chairman Jim Hall, asked about the skepticism, told reporters that much work remains to be done on radar data, and that the analysis had not been presented as definitive. "All of the radar data is preliminary," he said.

If the initial analysis proves correct, however, pilots and engineers are puzzled as to what would cause a plane to go through such a series of maneuvers. They questioned how the plane could withstand the gravitational forces of beginning a sharp climb from a rapid dive.

The keys to solving the mystery are the plane's cockpit voice recorder and flight data recorder, often called "black boxes" although they are almost always encased in an orange crash box.

Ships have heard the distinctive locator "pingers" of both recorders, sitting in wreckage more than 250 feet beneath the surface. However, it is not possible now to know whether they have usable data and locating them in the shredded wreckage and body parts on the ocean bottom will be no easy task.

If the Grapple is able to launch the remotely operated vehicle (ROV) Deep Drone, investigators will have their first look at the wreckage. The electrically operated ROV, made by Oceaneering International Inc.'s Advanced Technologies Group in Upper Marlboro, Md., has cameras, lights, sonar equipment and various other equipment. If it locates the recorders, it can grasp them and bring them to the surface.

Sutton said the decision whether to dive will be based solely on whether it would be safe for the ship's crew.

"We do not want to increase this tragedy any more than it is," he said.