The travel industry is still waiting to hear from airlines what impact the fuel supply problem could have on customers.
Airlines have been told they will receive 75 percent of what they had planned to use out of Auckland Airport after a shipment of A1 jet fuel was rejected at Marsden Point Terminal.
Travel Agents Association New Zealand president Brent Thomas said flights in the next few weeks were already at capacity.
"We're just not going to be able to move people around if flights get cancelled because you won't be able to put them on other flights that day or even that week because airlines have got little or no capacity between now and Christmas.
"Any plane that doesn't fly has a knock-on impact. One airline, one plane there and back - two flights disrupted is a minimum of 320 people ... that takes a long time to clear, and unlikely to be cleared in one day given the capacity issues," Thomas told Checkpoint.
"It's the busiest time of year of travel... flights are running at over 90 percent [full] ... we've got unprecedented demand with a lack of supply ... we're not back to full capacity domestically or internationally."
"We've got to wait and see exactly what will happen. There's going to be some anxiety out there," Thomas said.
"We are in a situation that we need to know from the airlines as soon as possible, but to be fair to them I don't think they've got all the information to make those decisions at this stage."
He expected international flights could get priority over domestic routes because: "You can't expect a plane to sit here and not fly back to its home land."
Long-term, the government needed to work with fuel companies and airlines to ensure security of supply, he said.
"That's the thing that the government's going to have to sit down with the airlines and airports and look at - what can be done?
"Marsden Refinery is no longer refining this kind of fuel ... supply chain from overseas does have issues, therefore have they got enough supply and enough storage in New Zealand is one of the questions they're going to have to answer."
Z Energy, which owns the dud shipment, signalled rationing may be required until December 20.
Energy chief executive Mike Bennetts said the fuel had passed tests on the ship but a potentially hazardous problem with "high conductivity levels" was identified as it was being unloaded.
"Aviation fuel quality is so important to get right clearly, that anything that is slightly off specification, we wouldn't take the risk of using it."
Chemistry experts have told RNZ that high conductivity in aviation fuel could increase the chance that a static electric charge builds-up, especially on long distance flight, which could lead to sparking and explosions.
No-one from either Air New Zealand or Jetstar was available for interview.
But both airlines told RNZ they were "working closely with their fuel suppliers" and were not making any changes to their schedule at this stage.
The Board of Airline Representatives of New Zealand chief executive Cath O'Brien said rationing would affect both domestic and international flights but airlines were working urgently to minimise the impact on customers.
"However, we all want to know as soon as possible what is being done to solve the shortage problem?
"While a shipment is due to arrive at Marsden Point on December 12, that was expected anyway. The impact shipment still creates a supply hole. Are additional supplies being sought? Or can the fuel supplier clean the rejected fuel?"
Fuel supply shortages could affect imports and exports, as airlines jettisoned freight to reduce weight, she said.
"However, they are going to be doing everything they can to avoid those kind of disruptions to freight or to passengers."
Another option for long-haul flights would be making more refuelling stops.
But that also required regulatory approval, hiring more ground handling staff and having to change staff rosters and scheduling, as well as making an allocated landing slot.
The organisation is calling on the Government to get better contingency plans in place.
Last month the Government announced plans to require importers and wholesalers to hold between three and four weeks of jetfuel, petrol and diesel.
Energy Minister Megan Woods said she hds been in talks with fuel companies about bringing forward fuel stockholding obligations, which were due to come into effect in 2024.
"At this stage we're not expecting to see major disruptions to passenger services."
She declined to be interviewed on Checkpoint.
Prime Minister Jacinda Ardern confirmed travellers had nothing to worry about.
"Christmas is not cancelled."