Huw Thomas, of England, eats his breakfast in his cot Monday at John F. Kennedy International Airport in New York. Before the volcano in Iceland brought European air travel to a halt, Thomas and his family were supposed to fly back to England from a vacation in New York on Friday, but now they are unsure of when they’ll be able to return home.

London ? Europe began allowing limited air traffic to resume, giving hope to millions of travelers stranded around the world when ash from a volcano in Iceland choked the jet age to a halt. Some flights resumed early today from Asia to southern Europe.

But further delays were likely because the eruption from the Icelandic volcano that caused days of aviation chaos was said to be strengthening and sending more ash toward Britain. British air traffic controllers kept London’s main airports closed today.

In Asia, a Japan Airlines flight from Moscow landed this morning at Tokyo’s Narita Airport, the first European flight to arrive since Friday night, airport spokesman Toru Motoyoshi said. On Monday, two Alitalia flights departed for Italy.

Singapore Airlines resumed flights early today to Barcelona and Rome, which joined Athens as the only European cities it flies to. But the airline said flights remained canceled to London, Zurich, Copenhagen and Frankfurt. Singapore’s Changi International Airport said 16 flights on five carriers were canceled today.

At South Korea’s Incheon International Airport, one flight departed for Istanbul, but all other flights to Europe were canceled today, said airport spokeswoman Kate Kang. She said about 250 passengers were stranded at the airport.

Three KLM passenger planes left Schiphol airport in Amsterdam on Monday evening during daylight under visual flight rules bound for New York, Dubai and Shanghai. An Associated Press photographer saw one jet taking off into a colorful sunset, which weather officials said was pinker than normal because of the ash.

European Union transport ministers reached a deal during a crisis videoconference to divide northern European skies into three areas: a “no-fly” zone immediately over the ash cloud; a caution zone “with some contamination” where planes can fly subject to engine checks for damage; and an open-skies zone.

Starting this morning, “we should see progressively more planes start to fly,” said EU Transport Commissioner Siim Kallas.

The German airline Lufthansa said it would bring 50 planeloads of passengers home.

But the optimism was tempered early today by a statement from the British National Air Traffic Service, which said “the volcanic eruption in Iceland has strengthened and a new ash cloud is spreading south and east towards the U.K.”

The service said Scottish airports should be open from 7 a.m. today, and other airspace over England may be reopened in the afternoon, but the open zone for flights would not extend as far south as London, where the country’s main airports are located.

Europe’s aviation industry — facing losses of more than $1 billion — criticized official handling of the disruption that grounded thousands of flights to and from the continent.

Visual flight rules allow a pilot to fly without reference to instruments, if weather conditions are good enough so the pilot can see landmarks and avoid any other aircraft. Those flights need to be under 18,000 feet, lower than usual altitude for commercial traffic.

Scientists have instruments that can both detect the presence of the ash and measure its concentration — information that can be relayed to pilots.

The airlines said test flights in recent days by airlines including KLM, Lufthansa and British Airways suggested planes can fly safely despite the ash. None of the flights reported problems or damage.

“The analysis we have done so far, alongside that from other airlines’ trial flights, provides fresh evidence that the current blanket restrictions on airspace are unnecessary,” said BA chief executive Willie Walsh. “We believe airlines are best positioned to assess all available information and determine what, if any, risk exists to aircraft, crew and passengers.”