LOS ANGELES, FEB. 2 -- An air traffic controller told a USAir Boeing 737 to land at Los Angeles International Airport Friday evening 72 seconds after directing a smaller twin-engine turboprop to taxi into takeoff position and wait on the same runway, the National Transportation Safety Board said tonight.

At the end of the board's first full day of investigation of the crash that killed 13 and left 20 unaccounted for, safety board member Jim Burnett refused to draw any conclusion from a reading of air traffic control tapes of conversations between a controller and the two aircraft. However, Burnett's narrative of the last few minutes before the two planes collided on Runway 24L drew a picture of a harried controller who apparently forgot that she had cleared the smaller plane onto the runway.

USAir Flight 1493's cockpit crew contacted the controller three times before she acknowledged and gave it clearance to land, Burnett said. That clearance came at 6:05:56 p.m. (PST) while SkyWest Flight 5569 had been cleared to enter the runway at 6:04:44. Burnett said the safety board will try to determine whether the controller was conversing with the two planes on separate radio frequencies or on one frequency that both planes' cockpit crews could have heard.

Burnett said the local controller who handled the two planes also was handling several other planes, including an Aeromexico flight with which she had "a somewhat difficult communication" and had to repeat several instructions. At one point, she asked two other aircraft if they were on Runway 24L but did not ask that of the SkyWest flight.

At 6:06:56, the taped conversation contains an "electronic squeal." Eight seconds later, a male voice exclaimed, "What the hell!"

The identity of who uttered the exclamation had not been determined, Burnett said.

All 10 passengers and the two pilots died in the SkyWest Fairchild Metroliner, according to a SkyWest spokesman. Burnett said five bodies from that plane, which he described as "almost obliterated," have been recovered from the runway. What is left of the Metroliner remains under the wreckage of the 737.

The USAir captain, Colin Shaw, 48, of Washington, D.C., also perished in the collision and fire, a USAir spokesman said. Twenty of the 89 passengers and crew on Flight 1493 from Syracuse, N.Y., Washington and Columbus, Ohio, remain unaccounted for, the spokesman said.

Burnett said the board had determined that the Boeing 737, landing in darkness with its landing gear down, struck the smaller plane from the rear 2,400 feet from the end of the runway where it first touched down, pushing the tangled wreckage 1,225 feet ahead and 620 feet to the left from the point of impact.

The larger aircraft snapped in two after hitting the Metroliner and dragging it into an abandoned airport fire station. Firefighters doused 20-foot-high orange flames with foam but did not begin to recover bodies from the site until daylight because of the danger of leaking fuel and halted the recovery operation again tonight because fuel remains in the planes.

The safety board's investigation will concentrate on lighting, both at the airport and on the smaller plane, according to Burnett, who said another aircraft's crew reported that just before the crash the SkyWest plane had its navigation lights and rotating red beacon burning but no takeoff light, strobe light or other lights. He said this was in compliance with Federal Aviation Administration regulations.

Investigators also will try to determine whether the airport's ground radar system was in operation at the time of the collision, Burnett said.

As investigators probed the twisted, blackened metal of the two planes, they expressed concern that the lack of flight recorders on the SkyWest plane, which was not required to have them, could hinder their investigation. Recorders were recovered from the USAir plane.

SkyWest spokesman Ron Reber said the Metroliner, scheduled to take off for Palmdale, Calif., 50 miles north at 5:45 p.m., was at least seven or eight minutes late. It was following normal procedures, he said, but "obviously something is very abnormal."

Safety board spokesman Alan Pollock said he was "disappointed to hear" that the smaller plane did not have the cockpit voice recorder and flight data recorder required on all aircraft with 30 or more seats, but not on the 19-seat commuter plane.

FAA spokesman Hugh O'Neill said a new regulation about to take effect will require installation of the voice recorders in smaller planes, although the data recorders, expensive to install, will still not be required.

Pollock said the safety board has expressed concern about collisions between aircraft on the ground, often caused by misunderstanding between controllers who are trained to focus on planes in flight and the lack of radar equipment to detect the position of aircraft when landing, taking off or taxiing. O'Neill said the FAA was studying the problem and expected to issue new rules to cover it.

The FAA has worked for years to produce a multimillion-dollar ground radar system but has been stymied by technical flaws. One prototype did not work in heavy rain, and another, installed in Pittsburgh, had a rapidly revolving antenna that tended to fly apart.

Burnett said 41 of the 68 known survivors on the 737 required no medical treatment. He said 15 of the 27 hospitalized were released. Of the 12 still being treated, two are in critical condition, according to a USAir official.

The official said most of the flight's crew members were based in Washington. The co-pilot, David Kelly, 32, is in intensive care with respiratory burns after inhaling smoke. Kelly served in the Air Force before joining USAir Oct. 30, 1988, and has logged 9,000 flying hours.

One flight attendant, Deanna Bethea, 23, is missing. The other attendants, William Ibarra, 23, the only Los Angeles-based crew member, and Washington-based Patricia Hodges, 26, and Vance Spurgeon, 26, were injured but survived. All had worked for USAir for about 1 1/2 years.

USAir Capt. Tom Kreamer, a member of the Air Line Pilots Association accidents investigation board who will review the cockpit voice recorder tape as part of the probe into the crash, said he had flown with pilot Shaw, who died in the accident, and described him as a "very good pilot. Very conscientious."

USAir spokeswoman Agnes Huff said Shaw joined the airline March 19, 1968, had been a captain since 1985 and had more than 15,000 hours of flight time.

Reber identified the Metroliner crew as pilot Andy J. Lucas, 33, of San Luis Obispo, and first officer Frank Prentice, 46, of Los Angeles. He said most of the passengers lived in California. SkyWest spokeswoman Kristan Norton said one of the passengers was Mike Fuller, 30, of Palmdale, who was the manager of the airline's Palmdale office.

Several survivors from the 737 said they had a hard, though normal landing, then felt a bump and saw flames bloom on the left side of the plane, apparently as it struck the Metroliner. Most escaped from emergency doors on the right side, away from the flames, but were coughing violently later in the makeshift recovery area.

Staff writers Gabriel Escobar and Martin Weil in Washington and special correspondent Jill Walker in Los Angeles contributed to this report.