Two pilots wrestled a knife-wielding woman to the floor after a terrifying mid-air ordeal in which she allegedly stabbed three people and tried to take control of the plane yesterday.

Asha Ali Abdille, 33, of Blenheim, who arrived in New Zealand as a Somali refugee, has been charged with hijacking a plane, wounding and two counts of injuring. The charge of hijacking carries a maximum penalty of life in prison.

Abdille will appear in the Christchurch District Court this morning.

The drama unfolded 10 minutes into the Air New Zealand/Eagle Air flight 2279 from Blenheim to Christchurch early yesterday.

Abdille, sitting in seat 1A directly behind the forward bulkhead, is alleged to have confronted the pilots.

One pilot suffered a cut to his hand, but details of how that happened have yet to be confirmed.

Canterbury police district commander Superintendent Dave Cliff said a mayday call was made at 7.40am from the 19-seater Jetstream 32, signalling a hijack and that a woman had attacked both pilots with a knife.

Abdille demanded the pilots take the flight to Australia, refusing a request from the pilots to return to Blenheim, Cliff said.

"There were also threats made to the safety of the passengers and claims made there were bombs on board the flight," he said.

The pilot tried to calm Abdille while she stood directly behind them during the flight holding a knife.

Two of the six other passengers on the flight also tried to calm Abdille; one of them -- a woman -- received a cut on the hand.

Abdille remained armed during the entire flight and continued to make threats, Cliff said.

When the plane came into land at Christchurch International Airport, the woman allegedly started moving the aircraft controls, he said.

"As part of the descent process, the pilots made a turn and the suspect lost balance and was no longer able to interfere with the controls," he said.

"She became silent but continued to have the knife in her possession. The aircraft landing was somewhat rough because of weather conditions."

When the plane had landed, the woman demanded passengers disembark through the front emergency exit, but the pilots refused.

She then directed them to open the pilot's window to allow the passengers to get out, but they convinced her the best way would be through the rear exit door, Cliff said.

The pilot then confronted the woman and wrestled her to the floor.

"The co-pilot, standing by the exit, saw the pilot wrestling with the suspect on the floor of the aircraft while (she was) still in possession of the knife," Cliff said.

The co-pilot helped the pilot to disarm the woman and in doing so his foot was cut. He threw the knife outside the aircraft as police Armed Offenders Squad dog handlers entered the plane and arrested the woman.

Another knife was found in her footwear, Cliff said.

The pilots and passengers had done an "extremely good job", he said.

Christchurch consultant radiologist Rauf Yousaf was waiting for a flight to Palmerston North when the drama began on the ground.

"Suddenly all these emergency vehicles converged on the plane -- fire trucks, the Armed Offenders Squad, guys with machineguns. It was all very unexpected for Christchurch," Yousaf said.

"Then they stormed the plane. They went in with dogs and guys in flak jackets."

The airport was effectively closed down for more than two hours while an army team swept the plane for two bombs the woman allegedly claimed were in her luggage.

Cliff said that because of the risk of bombs, a large area had to be cordoned.

The plane was towed to a hangar for a forensic investigation.

The Jetstream J32 is operated by Air National, which owns the plane and employs the pilots on behalf of Air New Zealand's Eagle Air.

Few of the planes are still in service and it is understood that progress on examining the plane was held up while the army waited for an engineer familiar with the aircraft before venturing into the hold, where it was feared the bomb was in the woman's luggage.

Blenheim Airport operations manager Kelly Byrne said her understanding was that the woman ``did not display any symptoms'' that may have alerted  staff when they boarded her.

Byrne said Blenheim Airport was not a security designated airfield.

Even if it was, it probably would not have made a difference, he said.

"Obviously what has happened is a concern, it makes the public uneasy, but we have remember it is a fairly isolated incident."

Air National sales and marketing manager Richard Bagnall said there was no door separating the cockpit from the cabin on the plane.

"That's something that needs to be reviewed in due course."

Air New Zealand deputy chief executive Norm Thompson said the incident had been "traumatic" for the airline.

The pilots' actions had been heroic and they had done a "miraculous" job in landing the plane.

"Getting that aircraft down under the circumstances was a fantastic piece of flying. Today has been a really traumatic experience."

The pilots, both experienced and in their 40s from Nelson, have received hospital treatment.

It is understood the pilot needed surgery to repair the damage to tendons caused while disarming the woman and was still in Christchurch Hospital last night. The co-pilot was released from hospital yesterday.

Thompson said their families had flown to Christchurch to be with them.

Passengers were getting support from Air New Zealand and Victim Support, he said.

Air New Zealand and the airline would conduct a full investigation into the incident in conjunction with the Civil Aviation Authority and the Aviation Security Service.

Asked if it might lead to access being blocked to flight decks or cockpits in all aircraft, Thompson said: "The investigation will be undertaken and we'll see what comes out of it."