PANGKALAN BUN, Indonesia (CBS News/CBSDC/AP) — After nearly a week of searching for the victims of AirAsia Flight 8501, rescue teams battling monsoon rains had their most successful day yet on Friday, more than tripling the number of bodies pulled from the Java Sea so far. An Indonesian navy official said some of the dead were still strapped to their seats.

Of the 30 corpses recovered in total, 21 were found on Friday, many of them by a U.S. Navy ship, according to officials.

The Airbus A320 carrying 162 passengers and crew went down Sunday, halfway into a flight from Surabaya, Indonesia’s second-largest city, to Singapore. Minutes before losing contact, the pilot told air-traffic control he was approaching threatening clouds, but was denied permission to climb to a higher altitude because of heavy air traffic.

It remains unclear what caused it to plunge into the sea, but CBS News’ Allen Pizzey reports that investigators are working on the principle that the pilots attempted a steep climb anyway, to avoid the weather, which could have stalled the jet’s engines.

Col. Yayan Sofiyan, commander of the warship Bung Tomo, told MetroTV five bodies pulled in by his crew were still fastened in their seats.

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Indonesian search and rescue chief Henry Bambang Soelistyo said he knew of only two victims found in their seats, but said a total of 30 bodies have been recovered.

Soelistyo said bad weather, which has hindered the search the last several days, was a worry. A drizzle and light clouds covered the area Friday, but rain, strong winds and high waves up to 13 feet were forecast until Sunday. Strong sea currents have also kept debris moving.

Soelistyo estimated the fuselage was at a depth of about 80 feet to 100 feet, and vowed to recover the bodies of “our brothers and sisters … whatever conditions we face.”

Rescue teams hope many of those on board are still within the fuselage, which has not been located.

Several countries involved in the massive effort are using sophisticated sonar equipment and metal detectors to scour the relatively shallow ocean floor for the wreckage — and the plane’s black boxes.

“We will focus on underwater detection,” said Soelistyo.

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The black boxes — or flight data and cockpit voice recorders — hold key data that will help investigators determine the cause of the crash, but they have yet to be recovered. When they are found, Pizzey reports they will be taken to Indonesia where government officials will decipher the data, and they’ve promised to make their findings public within three months of retrieving the boxes.

Pizzey said the body of a young boy was returned to his family on Friday after identification using dental records, finger prints and other means. The first victim from the aviation disaster to be identified was a woman whose body was returned to family members on Thursday.

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