The Carterton ballooning tragedy is the worst New Zealand air disaster since the Erebus crash in 1979.

The death of 11 people eclipses recent air tragedies including the 2003 crash of a Piper Chieftain near Christchurch Airport which killed eight people; and deaths of nine people in September 2010, when a small plane crashed just after taking off from the Fox Glacier air strip.

The biggest disaster involving a New Zealand-owned aircraft occurred on November 28, 1979 when an Air New Zealand DC10 crashed on Mt Erebus in Antarctica, killing all 257 passengers and crew.

Ballooning experts say ballooning is safe and whatever caused the Wairarapa disaster would be a "one-off"'.

Ballooning has been largely fatality free, though three tourists died in 1995 when they drowned after a flight operated by Balloon Adventures ditched in the sea off Waimairi Beach in Christchurch.

Balloon Aviation Association of New Zealand president Martyn Stacey said the industry was small - with six or seven operators - while the total number of balloons was between 60 and 70.



"In New Zealand we have very, very conscientious balloonists," he said.



Today's tragedy "is a real shock to everybody".



"The balloon was flying a normal flight in very good conditions, light winds. So something's happened that is out of the norm. We don't know what it is," Stacey said.



"Perhaps it hit something, power lines, I don't know - or something's gone wrong, something's failed in the aircraft."



Ballooning was a safe sport and New Zealand had one of the best safety records in the world.



Overseas, balloon crashes were sometimes caused by sudden weather changes, while hitting power lines was a problem in the United States.



Transport Minister Gerry Brownlee expressed his condolences on behalf of the Government to the families and loved ones of the 11 people who lost their lives in the Wairarapa tragedy.



"We are deeply sorry to learn of this tragic accident and our hearts go out to those who are now mourning the loss of life."



Rules for the commercial operation of hot air balloons were part of a recently completed review into adventure tourism, Brownlee said.



"Experts will be looking to learn any lessons from the investigations which have begun today which can help improve safety for others in the future."



Other significant New Zealand air disasters or crashes which have claimed five or more lives include:

July 3, 1963 - NAC DC3 crashes in the Kaimai Ranges, 25 dead.

Jan 2, 1986 - Cessna crashes on takeoff near Picton, seven dead.

Oct 4, 1986 - Cessna hits powerlines and crashes into sea in Tory Channel, eight dead.

May 12, 1988 - Piper crashes into hills near Wanganui, nine dead.

Feb 14, 1989 - Helicopter hits power lines over Shotover River and crashes, five dead.

Aug 8, 1989 - Britten-Normander Islander crashes between Milford Sound and Wanaka, 10 dead.

Dec 39, 1989 - Two Cessnas collide over Milford Sound, one crashes, seven dead.

Oct 25, 1993 - Nomad 23 crashes near Franz Josef Glacier, nine dead.

Oct 29, 1994 - Helicopter crashes near Fox Glacier, seven dead.

Mar 29, 1995 - Beechcraft crashes near Hamilton, six dead.

Jun 9, 1995 - Ansett New Zealand Dash 8 crashes near Palmerston North, four dead.

Jan 29, 1996 Cessna Caravan crashes near Picton, five dead.

Jan 3, 1997 - Cessna crashes near Queenstown, six dead.

Aug 19, 1998 - Cessna 402 crashes in Foveaux Strait, five dead.

Apr 12, 1999 - Helicopter crashes at Lake Poteriteri, five dead.

Apr 18, 1999 - Cessna floatplane crashes in Fiordland, five dead.

Mar 8, 2000 - Helicopter crashes at Manapouri, six dead.

Jan 19, 2001 - Cessna 207 crashes in Fiordland, six dead.

Jun 6, 2003 - Piper Chieftain crashes near Christchurch Airport with Crop and Food staff on board, eight dead.

September 4, 2010 - Fletcher FU24-95 crashes near Fox Glacier air strip, nine dead.

Nov 27, 2008 - Air New Zealand Airbus A320 crashed on a test flight in southern France, killing all seven on board.