Pilot Richard Jowsey said the call was heard at the Parakai Airfield.
"The guys received the call. They were totally shocked and very concerned. He [the pilot] said, 'Mayday, mayday, mayday.' He said his engine had failed and they were going to put down using the emergency landing procedure," Mr Jowsey said.
"That mayday call shook them up to hell at the airfield. It was pretty broken up and scratchy."
The mayday call was also heard by an instructor at the Dargaville Aero Club, where the plane was due to land.
Murray Foster, a friend of the men and their flight instructor, said a colleague also heard the call.
"They said it sounded like the guys, but it was very weak. I called them back on the radio to see if I could contact them ... I couldn't."
Mr Foster said the men had been very excited about their trip away.
They landed in Paraparaumu and stayed with friends for a night, before driving to the Ohakea air force base, near Bulls, for the annual air show.
"It was their own plane. They only just bought it - they'd had it about a month or six weeks. [The pilot] had owned several planes before and he was experienced," he said.
"They did a lot of flight planning; their planning was really good. I helped them with it and they were very particular about their planning.
"They were really good guys ... It's very, very sad."
One pilot was experienced, the other man was still in training.
The pair stayed with Mr Foster for several days before they set off on Friday.
Yesterday, while the qualified pilot flew the plane, the trainee sent Mr Foster updates by text about their trip.
"The first text said they were going okay. The next one, from Raglan, said they were worried about the weather in Dargaville. I gave them the okay and said the conditions were fine.
"They said they'd be here at lunchtime.
"I got another text saying there was too much noise and they couldn't ring me from the plane. And then they didn't arrive."
The Rescue Co-ordination Centre responded to the mayday calls by dispatching the Northland Emergency Services Trust helicopter to the last known location of the Zenair Zodiac.
As its crew searched the area, a farmer found the wreckage in a paddock near his house.
Chief pilot Pete Turnbull said the plane was badly damaged.
"There was still a small fire burning ... There were no signs of life."
The farmer and his wife were upset by the tragic find.
Emergency services converged on their property and moved quickly to cover the wreckage, with the bodies still inside, with tarpaulins.
The wife said it was a terrible situation, but out of respect for the victims' families she did not want to speak about the accident.
Mr Jowsey, an experienced pilot who knows the area well and has flown over it many times, suspected that as the plane glided in for the emergency landing, it was struck by a "king wave" of wind.
The area is known for its gusty conditions, he said, and while the pilot appeared to pick the "perfect spot" to land, the wind might have been the fatal factor.
"It was probably a combination of bad weather and bad luck. It's horrible. It would have been a hell of a slam ... It would have been quick."
From what he heard on the mayday call, Mr Jowsey did not believe the crash was the result of pilot error.
"He did all the right things, I think. He's died bravely trying to save his plane and passenger.
"Were it not for the easterly gusty conditions, he would have probably walked away from that."
Crash countdown
9am yesterday
The Zenair Zodiac takes off from Paraparaumu.
9am-noon
The men text a flight instructor, giving updates on their progress.
Noon
They are reported missing after failing to arrive in Dargaville on time and after mayday calls are made from the plane.
1pm
The Northland Emergency Services Trust helicopter is dispatched to search for the Aucklanders.
2pm
The men are found dead in the wreckage in a farm paddock at South Head.
