After almost a week of paralysis caused by ash from a volcanic eruption in Iceland, European skies are slowly re-opening to flights.
But with more than 95,000 flights cancelled across Europe in the past week, officials warn it might take weeks to get all stranded passengers where they want to go.
Britain has reopened its airspace in the latest easing of the shutdown following the eruption that caused six days of travel chaos.
London's Heathrow Airport reopened just before 2100 GMT on Tuesday, with the first British Airways flight arriving from Vancouver.
Air New Zealand has put on extra flights in an effort to clear the backlog of several thousand of its stranded passengers around the world.
The airline resumed flights to and from London on Wednesday, however, it reiterated to customers that the situation in Europe could change and flights may be delayed or disrupted at any point.
Air New Zealand says stranded passengers in Hong Kong and Los Angeles will have priority, followed by those with existing bookings and then customers in chronological order from their original point of delay.
The airline has seven flights departing on Wednesday and Thursday, three of which are additional to its normal schedule. Two flights left Auckland for London on Wednesday night.
Air New Zealand's international group general manager, Ed Sims, says the airline hopes to clear the backlog of between 3000 and 4000 passengers by the end of next week. Passengers can still defer travel without penalty or apply for a full refund.
Many flights in Europe expected to go ahead
In Europe, the continent's air traffic control agency Eurocontrol says it expects up to 75% of flights across Europe to go ahead on Wednesday out of a weekday total of almost 28,000.
However, Heathrow Airport remained quiet, despite the reopening of British airspace. Staff say the situation in relation to flights is changing all the time.
British Airways says it plans to fly all long-haul flights from Heathrow on Wednesday.
Some flights from other airlines had already left Paris, Amsterdam and Frankfurt, while airports in Italy, the Netherlands, Poland, Switzerland, and some Scandinavian countries have also opened. Germany ended its flight restrictions on Wednesday.
Flights have left Australia for Europe for the first time since last Thursday. British Airways, Singapore Air and Virgin Atlantic flights left Sydney on Wednesday afternoon headed for London or Frankfurt.
The first Qantas flights will not leave Australia until Thursday, although the airline began flights from Bangkok and Singapore to Europe on Wednesday afternoon.
NZ to waive permit fees
Immigration Minister Jonathan Coleman says fees will be waived for people needing permits to remain in New Zealand due to flight delays to Europe.
Dr Coleman says fees will also be waived for travellers who cannot get to New Zealand and who have visas to New Zealand that are about to expire.
Anyone who has paid for a further visa or permit in the past few days may be eligible for a refund and should contact Immigration New Zealand, he says.
Ash forecast to head towards Arctic
Ash clouds from the Iceland volcano which have caused the closure of European airspace are expected to change direction and head north towards the Arctic later this week.
The World Meteorological Organisation says a change in wind direction and showers should help to wash out the ash at low levels.
Scientists in Iceland say the Eyjafjallajokull volcano is producing more lava, and the ash plume is shrinking, although it remains changeable.
The United Nations says it will lead moves to develop global standards for determining the safety risks posed by volcanic ash in the air.
The UN's International Civil Aviation Organisation says a global system monitoring the dangers had been operating smoothly. However, it says the unprecedented disruption means there is a need for a global network to routinely determine safety levels.
The organisation says it will still be up to governments to make the final decisions about safety.
Handling of flight restrictions questioned
The reopening of Europe's airspace is not quieting concerns about how the initial flight restrictions were handled.
Airlines have carried out test flights through the volcanic ash and reported no problems, raising questions about whether the flight restrictions that have caused travel chaos have been necessary.
Air traffic authorities in Britain on Wednesday explained their sudden decision to allow flights to go ahead, saying they had been waiting to analyse all the data from test flight before deciding which parts of the airspace were safe.
British Airways estimates it has been losing over $US20 million a day because of the flight ban. Now it appears to be easing, the travel industry's fight for compensation, if not a full-scale bailout, is expected to step up a gear.
Asia business woes
In a sign of the impact of the volcanic ash crisis on Asia's export-driven economies, Japanese car giant Nissan says it is suspending several production lines due to the shortage of parts from Ireland. Honda will also partly halt production.
In China, blocked shipments of manufactured products are reported to be piling up in China.
South Korea is stuck with hundreds of thousands of mobile phones, while heaps of clothing bound for Europe are sitting idle in Bangladesh.
