By MICHAEL WEISSENSTEIN and PORFIRIO IBARRA RAMIREZ
MEXICO CITY (AP) - The plane carrying Mexican-American music superstar Jenni Rivera plunged almost vertically from more than 28,000 feet and hit the ground in a nose-dive at a speed that may have exceeded 600 miles per hour, Mexico's top transportation official said Tuesday.
In the first detailed account of the moments leading up to the crash that killed Rivera and six other people, Secretary of Communications and Transportation Gerardo Ruiz Esparza told Radio Formula that the twin-engine turbojet hit the ground 1.2 miles from where it began falling.
"The plane practically nose-dived," he said. "The impact must have been terrible."
Ruiz did not offer any explanation of what may have caused the plane to plummet, saying only that "The plane fell from an altitude of 28,000 feet ... It may have hit a speed higher than 1,000 kph (621 mph)."
Ruiz said the pilot of the plane, Miguel Perez Soto, had a valid Mexican pilot's license that would have expired in January. Photos of a temporary pilot's certificate issued by the U.S. Federal Aviation Administration and found amid the wreckage said that Perez was 78.
Ruiz said there is no age limit for flying a civil aviation aircraft, though for commercial flights it's 65. In the United States it's unusual for a pilot to be 78.
The extremely high speeds at which Learjets can fly _ close to the speed of sound _ make them especially challenging to fly, pilots and safety experts said.
"These aircraft require an awful lot of skill to fly and don't leave a lot of margin for error," said Lee Collins, a cargo airline pilot and executive vice president of the Coalition of Airline Pilot Associations in Washington.
He said that in situations in which a pilot loses control of an aircraft, the plane could "get into a high-speed dive and inadvertently go through the speed of sound." Collins said.
One possible cause for a nose dive like the one described by Mexican officials would be a drastic failure of the flight controls _ the ailerons, elevators and stabilizers, said former NTSB board member John Goglia, an aviation safety expert.
"High performance airplanes by their nature have issues," Goglia said. "The airplane flies faster than the human mind (can keep up) sometimes. ... It takes a lot of skill to stay in front of that airplane."
Mexican authorities were performing DNA tests Tuesday on remains believed to belong to Rivera and the others killed when her plane went down in northern Mexico early Sunday morning.
Investigators said it would take days to piece together the wreckage of the plane carrying Rivera and find out why it went down.
The U.S. National Transportation Safety Board said it was sending a team to help investigate the crash of the Learjet 25, which disintegrated on impact in the rugged terrain in Nuevo Leon state in northern Mexico.
Human remains found in the wreckage were moved to a hospital in Monterrey, the closest major city to the crash, and Rivera's brother Lupillo was driven past a crowd of reporters to the area where the remains were being kept. He did not speak to the press.
A state official, speaking on condition of anonymity because of the ongoing investigation, said investigators were testing DNA from the remains in order to provide families with definitive confirmation of the deaths of their loved ones.
"We're in the process of picking up the fragments and we have to find all the parts," Argudin told reporters on Monday. "Depending on weather conditions it would take us at least 10 days to have a first report and many more days to have a report by experts."
In an interview on Radio Formula, Alejandro Argudin, head of Mexico's civil aviation agency, said Mexican investigators weren't sure yet if the Learjet had been equipped with flight data recorders. He also said there had been no emergency call from the plane before the crash. In the U.S., the plane would not have been required to have a flight data recorder or a cockpit voice recorder.
Fans of Rivera, who sold 15 million records and was loved on both sides of the border for her down-to-earth style and songs about heartbreak and overcoming pain, put up shrines to her with burning candles, flowers and photographs in cities from Hermosillo, Mexico to Los Angeles.
Some Spanish-language radio stations played her songs nonstop.
A brother, Juan Rivera, as well as mother Rosa Saavedra, still held on to hope that she would be found alive.