The nearly week-long air traffic jam is showing signs of movement as European airspace is slowly opening. EUROCONTROL reports that nearly half of the 28,000 flights it normally handles will be back in the air as of Tuesday, the 20th. It's a break in the ash cloud that gives stranded passengers hope, however reports out of Iceland indicate that there could be more ash-related disruptions in the days to come.

EUROCONTROL maintains a Web site for its Central Flow Management Unit (CFMU) and offers a Network Operations Portal where you can view the latest information regarding the volcanic ash (see Network Headline News section of the site). UK airspace was set to reopen Tuesday night which would bring one of the busiest airports in the world, London's Heathrow Airport, back to life. British Airways planned to receive 25 flights into Heathrow by Tuesday night as flights from the west coast of the United States, Africa, India and other locations in Asia began to arrive. The Air Transport Association (ATA), which supports airlines in North America, has provided updates to the number of flights cancelled compared to a normal operating day. You can view the updates here.

France, Germany and Italy have reopened their respective airspaces, however Germany's restrictions on Tuesday limited flights to low altitudes under visual flight rules (less reliance on instruments) to protect the sensitive equipment from potential damage at higher altitudes. Norway opened part of its airspace near Bergen but Finland airspace will remain closed until Wednesday morning, the 21st.

The issue of ash is a perplexing one. Many passengers have asked why planes could not fly at lower altitudes to avoid the ash. The complexity of weather adds to the frustration. Though the ash "layer" could be found at a certain altitude at any given moment, planes would need to traverse that layer on their way up or down. In addition, the ash does not stay at one altitude. If it drifts low enough, it could become too risky for planes to take off or descend through it.

For the latest updates, visit:

• EUROCONTROL
• CFMU NOP Portal
• Air Transport Association (ATA)
• Civil Air Navigation Services Organization (CANSO)
• NATS: The UK's leading Air Navigation Services Provider

Source: CNN; Air Transport Association; Photo: NASA