Reuters reported that the plane was an Airbus 320-200. It had 155 passengers and seven crew members, according to The New York Times.
Air traffic control lost contact with the plane after it asked for an unusual route. The plane had been scheduled to land at 8:30 a.m. Singapore time.
http://www.buzzfeed.com/...
I'm assuming the indirect line is the requested "unusual route".
From an AirAsia Facebook posting.
AirAsia Indonesia regrets to confirm that flight QZ8501 from Surabaya to Singapore has lost contact with air traffic control at 07:24hrs this morning.
At the present time we unfortunately have no further information regarding the status of the passengers and crew members on board, but we will keep all parties informed as more information becomes available.
The aircraft was an Airbus A320-200 with the registration number PK-AXC.
At this time, search and rescue operations are in progress and AirAsia is cooperating fully and assisting the rescue service.
From the above link, part of the response from Civil Aviation Authority of Singapore (CAAS):
An Indonesia AirAsia aircraft, QZ8501, scheduled to arrive at 0830 hours local time from Surabaya, lost contact with Jakarta air traffic control at 0724 hours local time today. Singapore air traffic control was informed of this loss of contact at 0754 hours by Jakarta air traffic control. The aircraft was in the Indonesian Flight Information Region (FIR) when contact was lost, more than 200 nm southeast of the Singapore-Jakarta FIR boundary.
Search and rescue operations have been activated by the Indonesian authorities from the Pangkal Pinang Search and Rescue office.
The Singapore Rescue Coordination Centre (RCC), managed by the Civil Aviation Authority of Singapore (CAAS) and supported by various agencies, including the Republic of Singapore Air Force (RSAF) and the Republic of Singapore Navy (RSN), has also been activated and has offered help to the Indonesian authorities. Two C130s are already on stand-by for this purpose. We remain ready to provide any assistance to support the search and rescue effort.
10:01 PM PT:
The captain in command had a total of 6,100 flying hours and the first officer a total of 2,275 flying hours, said AirAsia.
The aircraft, which underwent its last scheduled maintenance on 16 November 2014, was on the submitted flight plan route and was flying at 32,000 feet before it asked to fly at 38,000 feet to avoid clouds, Reuters reports.
QZ 8501 was between the Indonesian port of Tanjung Pandan and the town of Pontianak, in West Kalimantan on Borneo island, when it went missing.
10:33 PM PT: From jan4insight's comment below: unconfirmed wreckage sightings.
http://www.dailykos.com/...
11:19 PM PT: The link has further info, mostly about people who were planning on greeting arriving passengers.