About 160 Defence Force personnel will miss the military funeral for their colleagues killed in the Anzac Day helicopter crash.

The servicemen and women - who travelled to Turkey for the Gallipoli commemorations - tried to change their flights as they are due back Friday and the funerals are on Thursday.

However, it has proved impossible to change the itinerary to get back in time.

Some of those travelling knew the dead men well and missing the funerals has added to the upset.

Flight Lieutenant Hayden Peter Madsen, 33, Flying Officer Daniel Stephen Gregory, 28, and Corporal Benjamin Andrew Carson, 25, were killed when their Iroquois hit a hill at Pukerua Bay, about 40km north of Wellington, as it headed from Ohakea air base for an Anzac Day dawn flypast in Wellington.

Sergeant Stevin Iain Creeggan survived but was badly hurt and underwent surgery. He was in a stable condition at Wellington Hospital yesterday with his parents and partner at his bedside.

Funeral plans would be confirmed today, Royal New Zealand Air Force spokesman Squadron Leader Kavae Tamariki said.

A military funeral would be held at Ohakea at 1.30pm on Thursday, but the families were yet to decide if they would also hold three separate private funerals, he said.

Prime Minister John Key was due to return early to New Zealand today from Turkey, where he had been at Anzac Day services to commemorate the 95th anniversary of the Gallipoli landings.

Mr Key said he was "shocked and saddened by this tragic event".

"My thoughts are with the families of the victims, the family of the injured man, and the entire New Zealand Defence Force," he said in statement from Gallipoli.

Air force chief Air Vice-Marshal Graham Lintott said an investigation into the crash was ongoing and could take some time.

Investigators would photograph the site and map it out before the wreckage was flown out, possibly by another Iroquois.

The crash site would then be recreated back at Ohakea for more analysis, AVM Lintott said.

Media attention on the age of the helicopter was a "red herring" and the air force had full confidence in its airworthiness, he said.

The air force acquired its first Iroquois in 1966.

"Every three or four years they have a major depot-level servicing, and during their life, all of the components will have been replaced several times," AVM Lintott said.

Yesterday's crash was the fifth by an Iroquois since they were first introduced in 1966. AVM Lintott did not know if the Iroquois that crashed yesterday had crashed previously.

"But if it's been crashed and repaired, it's like a brand new aircraft anyway. So that wouldn't be a factor."

The deceased's commanding officer, Wing Commander Russell Mardon, yesterday said the men were "fantastic individuals, each and every one of them".

"I consider them not only colleagues or members of the squadron but also friends," he told Campbell Live.

The men had "died doing what they loved", Wg Cdr Mardon said.

"We're proud of the boys, and we're very proud of the unit."

The No 3 Squadron was "very much in a state of shock".

"Those friendships and links go all across the squadron. The culture and the camaraderie that we have is something special, and it's what we're relying on right now to get through this," Wg Cdr Mardon said.

- Claire Trevett and NZPA