Prime Minister John Key spent half an hour in Wellington Hospital with the only survivor of the Anzac Day Iroquois crash on the eve of the funeral for his three colleagues.

Yesterday's service followed an unofficial send-off by the men's comrades, which involved an old Air Force tradition of setting a piano alight.

Flying Officer Dan Gregory, 28, Flight Lieutenant Hayden ("Muddy") Madsen, 33, and Corporal Ben Carson, 25, were killed when their helicopter crashed in Pukerua Bay, north of Wellington, on Sunday.

Their coffins were flown to the base in separate Iroquois helicopters before the full military funeral at Ohakea Air Base in Manawatu.

More than 2000 Air Force and defence personnel joined the airmen's families in a service led by Air Force chaplain Wing Commander Ross Falconer.

Among those who paid tribute were Mr Key and Wing Commander Russell Mardon, chief of No 3 Squadron.

On Wednesday, Mr Key spent 30 minutes chatting with Sergeant Stevin Creeggan, who was seriously injured in the crash.

The Prime Minister said yesterday that the tragedy had been felt deeply by New Zealanders.

"New Zealand has lost three fine servicemen, and family have lost a loved one.

"Your loss is still sore ... You need to know New Zealand grieves with you."

The airmen had died "representing their country with pride, courage and distinction", Mr Key said.

"They are lost, but never forgotten."

A member of No3 Squadron told the crowd the airmen had died as brothers-in-arms.

"I have comfort in the knowledge that Muddy, Dan and Ben went together. They will always be a crew. Go well, brothers."

After the service, the coffins were taken to another hangar for private family services.

A 100-person guard of honour and firing party lined the procession, and the Air Force haka was performed to farewell the men.

Meanwhile, two photos of a piano burning with three beer bottles sitting on top, with uniformed spectators surrounding it, has been posted on a tribute page set up on the social networking site Facebook.

The burning of a piano is thought to be an unwritten tradition when there has been a death in the Air Force as a way to farewell the fallen.

A piano-playing pilot in the Royal Air Force in World War II entertained his mates as a way to remember fallen comrades.

However, he was killed and his buddies decided that if he couldn't play the piano any more, nobody would, so they dragged it outside and set it alight.