Fingers crossed for the souls on board.

BBC News

I am surprised that a commercial flight could 'disappear' for so long. I was under the impression that they were monitored very closely and that a rescue would be put in place within minutes.

What is the the typical time for locating such a downed flight?

"Vanish" is a bit of a journalistic exaggeration.

News reports are that the data links from the plane and radar give a good location where the plane went down. Radar tracked "a plane" (presumably the plane in question) "descending" at that location. The location is over the ocean, and "so far" no wreckage has been sighted. Reports are that there were no distress calls call from the aircraft, but that the data links from the aircraft have the same data that would be on the flight data recorders, so they should indicate if it was something mechanical. The data links are automatically recorded.

The are images from flightradar24 that show where the aircraft stopped transmitting, and they were shown on the news about 30 minutes ago; I don't know if these images are available on the flightradar24 website.

That's going to depend on where the flight is. Over the continental United States, I do not believe that there's any airspace where a commercial flight is not both monitored by radar and in contact with air traffic control. Over open ocean is a different story, with large stretches where a pilot has no contact with anyone other than possibly other air traffic.

VIETNAM SPOTS OIL SLICKS IN HUNT FOR MISSING JET.

Commercial airliners are usually not tracked by radar, instead an on-board transponder indicates altitude, attitude, heading, speed and the plane's ID code. At a certain altitude, depending on the distance from the nearest airport, transponder signals will be lost. Hence the rather large search area.

Big sea - small plane. At night, as well.

Locally we experienced a similar incident more than ten years ago when an Alaska Airlines flight plunged into the sea about three miles off Anacapa Island. This happened about 4:30 in the afternoon, and was witnessed by people on Anacapa Island and by boats in the vicinity, hence a much faster response.

And to think that I was going to get in a tiny bush plane. I wish them the best, but their odds of survival are exceedingly slim.

Just saw this

http://www.fieldline.com/Products/alpha-ops-internal-frame-pack/44

The report that two of the passengers listed on the flight appear to be using European passports reported stolen in Thailand. Does raise the possibility of terrorism as a possible cause.

True, it does raise a suspicion. The problem is that terrorists want to make a point with their terror: after this many hours, no terrorist group has claimed responsibility, even if it is just an opportunistic claim (i.e. they claim credit, but didn't actually do anything).

We need more facts:

"I have no data yet. It is a capital mistake to theorize before
one has data. Insensibly one begins to twist facts to suit
theories, instead of theories to suit facts."
- Sherlock Holmes in “A Scandal in Bohemia”, by Sir Arthur Conan Doyle

In this case no news is definitely not good new, I'm afraid. Starting to look like the plane crashed into the sea off Viet Nam. Hopefully I'm wrong and it will turn up but...