AirAsia Indonesia flight QZ8501 to Singapore missing

"This is a massive shock to us and we are devastated by what has happened. It's unbelievable."

He said the captain had more than 20,500 flight hours, almost 7,000 of them with AirAsia.

The flight left Surabaya in eastern Java at 05:35 local time (22:35 GMT) and was due to arrive in Singapore at 08:30 (00:30 GMT).

The missing jet had requested a "deviation" from the flight path to avoid thick storm clouds, AirAsia said.

Indonesia's transport ministry said the pilot had asked permission to climb to 38,000ft (11,000m).

Ministry official Djoko Murjatmodjo said the request "could not be approved at that time due to traffic, there was a flight above, and five minutes later [flight QZ8501] disappeared from radar".

At the scene: Saira Asher, Changi Airport, Singapore

Flight QZ8501 was supposed to arrive early this morning. Hours later the families of the passengers gathered here have very little information.

Airport officials are keeping them well away from the media and trying to make them comfortable.

The scenes at Changi are reminiscent of those in Kuala Lumpur immediately after MH370 went missing in March: anxious relatives waiting for any news on their loves ones, a media frenzy, but no answers.

At the scene: Alice Budisatrijo in Surabaya airport

A few hours ago many of the relatives at the crisis centre in the airport still seemed calm - glued to their phones, perhaps trying to find any news of the plane or stay in touch with friends and loved ones

But more than 12 hours since the plane took off they are looking increasingly worried. Officials still have no idea what happened to the aircraft. The governor of East Java, Soekarwo, the mayor of Surabaya, Tri Rismaharini, and the chief executive of AirAsia, Tony Fernandes, have come to talk to the relatives to assure them that all is being done to locate the missing Airbus.

This has been a difficult year for aviation in Asia: Malaysia's national carrier Malaysia Airlines has suffered two losses - flights MH370 and MH17.

Flight MH370 disappeared on a flight from Kuala Lumpur to Beijing in March with 239 passengers and crew. The wreckage, thought to be in southern Indian Ocean, has still not been located. MH17 was shot down over Ukraine in July, killing all 298 on board.

The Airbus, pictured here on an earlier flight, disappeared about an hour after takeoff

There was a similar scene at the flight's intended destination in Singapore

The flight arrivals board at Changi Airport in Singapore, where the AirAsia flight was due

There were 155 passengers on board, the company said in a statement:

• 138 adults, 16 children and one infant
• Most on board were Indonesian
• Several were from other countries: one UK national, a Malaysian, a Singaporean and three South Koreans
• The BBC understands that the British national is Chi-Man Choi
• Two pilots and five crew were also on board - one French, the others Indonesian

The plane in question was delivered to AirAsia in 2008, has flown 13,600 times, covering 23,000 hours, and underwent its last maintenance on 16 November.

AirAsia has set up an emergency line for family or friends of those who may be on board. The number is +622 129 850 801.

Dozens of passengers' relatives have been gathering at Juanda airport in Surabaya and Singapore's Changi airport to hear news.

AirAsia Group facts

• Low-cost airline group with main hub in Kuala Lumpur, Malaysia. Founded in 2001
• AirAsia Group services now comprises eight affiliates, including AirAsia Indonesia
• Group employs more than 15,000 staff
• Operates fleet of more than 150 Airbus A320 aircraft with 200 more on order
• Flies to about 100 destinations in some 15 countries. Carried almost 8 million passengers in 2013
• Tony Fernandes has been the group's CEO since December 2001

AirAsia profile

Tony Fernandes profile

Tony Fernandes has been CEO since 2001

Changi airport authorities have set up a holding area for relatives. It said 47 had arrived and care officers and counsellors were on hand to provide support.

AirAsia Indonesia operates domestic flights round the Indonesian archipelago as well as international services to Malaysia, Singapore, Australia and Thailand.

AirAsia Indonesia, along with other Indonesian airlines, was banned from flying to the European Union in 2007 due to safety concerns but this was lifted in July 2010.

The AirAsia group has previously had no fatal accidents involving its aircraft.