[PghBaldy]

Some unnamed US official is saying they think it is at the bottom of the Indian Ocean. Implication per reporting that they strongly believe this.

[PghBaldy]

"There is probably a significant likelihood" that the aircraft is now on the bottom of the Indian Ocean, the official said, citing information Malaysia has shared with the United States."

http://www.cnn.com/2014/03/13/world/asia/malaysia-airlines-plane/