All European airspace higher than 20,000 feet is open for flying today, a week after a massive volcanic ash cloud settled over the continent. But the airlines are physically and financially far from home free, according to scientists and industry officials.
"The best-case scenario is the worst is over, but I have my doubts," author and physicist Michio Kaku told "Good Morning America" today. "The more likely scenario is that this is a repeat of 1821, where for 14 months that very same volcano sputtered. We'll have to look for windows to shoot airplanes through or over.
"It's going to sputter for quite a while," Kaku said.
Least likely, the worst-case scenario, Kaku said, was that the eruption in Iceland could set off "Big Brother," referring to Iceland's Katla volcano, which Kaku said could be 10 times more powerful than the current eruption. Other scientists in Iceland told "GMA" further eruptions weren't likely to cause a similar ash cloud since this eruption occurred during unusual wind conditions and the ash was particularly fine, allowing it to be carried by the wind more easily.
The airline industry has already lost an estimated $1.7 billion, according to the International Air Transport Association. Eurocontrol, Europe's air safety organization, said the ash cloud caused the cancellation of more than 100,000 flights since last week, affecting millions of passengers every day.
In response, the IATI requested governments examine ways to compensate airlines for lost revenue, similar to how the U.S. government did following the terrorist attacks of Sept. 11, 2001.
"I am the first one to say that this industry does not want or need bailouts. But this crisis is not the result of running our business badly," said IATI Director General Giovanni Bisignani in a statement. "It is an extraordinary situation exaggerated with a poor decision-making process by national governments. The airlines could not do business normally. Governments should help carriers recover the cost of this disruption. ... This crisis is an act of God -- completely beyond the control of airlines."
If there are more ash cloud plumes, there is not much airplanes can do at the moment to deal with them, ABC News aviation consultant John Nance told "GMA."
"There's nothing that we're going to do to get airplanes to fly safely through ash clouds. ... We need better methods to find out where it is," Nance said. "Our radar can't pick this up. ... We were totally unprepared for this."
More than 75 percent of air traffic is expected to operate today, totaling an estimated 21,000 flights out of the usual 28,087, Eurocontrol said. But it could still be weeks before airlines catch up to the backlog of flights from earlier cancellations.
The last major European hub to open, London's Heathrow airport, allowed its first flight to land Tuesday night.
Airports in Britain had stayed closed longer than other European hubs, due to the threat of more ash clouds blowing into British airspace.
The volcano in southern Iceland is still spewing smoke and lava, but the ash plume is lower than it previously was, posing less threat to high-flying aircraft. One of Iceland's top scientists, Magnus Gudmundsson of Iceland University did note, though, that scientists "cannot be sure" the situation will continue to improve.