Europe began to emerge from a volcanic cloud Monday, allowing limited air traffic to resume and giving hope to millions of travelers stranded around the world when ash choked the jet age to a halt.
Even then, however, the eruption from the Icelandic volcano that caused the five days of aviation chaos was said to be strengthening and sending more ash toward Britain, which could make it unlikely that London airports would reopen today.
Three KLM passenger planes left Schiphol airport in Amsterdam 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 due to 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.
The German airline Lufthansa said it would bring 50 planeloads of passengers home.
But the optimism was tempered Monday night by a statement from the British National Air Traffic Service, which said the eruption of the volcano has strengthened and a new ash cloud was spreading toward Britain.
The service said that airspace over some parts of England may be reopened this afternoon but that the open zone for flights may not extend as far south as London, where the country's main airports are located. It also indicated that Scotland's airports and airspace can reopen as planned this morning but said the situation in Northern Ireland was uncertain.
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.