[maggief]

The aircraft was between the Indonesian port of Tanjung Pandan and the town of Pontianak, in West Kalimantan on Borneo island, when it went missing, Joko Muryo Atmodjo, air transportation director at the Transport Ministry, told a news conference.

The aircraft had been flying at 32,000 feet and had asked to fly at 38,000 feet to avoid clouds, he said.

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http://economictimes.indiatimes.com/articleshow/45665525.cms?utm_source=contentofinterest&utm_medium=text&utm_campaign=cppst

[maggief]

Yahoo Singapore @YahooSG 5m5 minutes ago

#QZ8501: 6 ships and 2 helicopters have been deployed to location where aircraft lost contact. @kemenhub151

[zipper]

The aircraft had been flying at 32,000 feet and had asked to fly at 38,000 feet to avoid clouds

The higher altitudes put them closer to both their stall speed and overspeed mach number, a.k.a. puts them into a "coffin corner".

Smaller airpeed margin, less room for error in turbulence.