Airlines are on alert as one of Iceland’s biggest volcanoes rumbles to life, threatening ash clouds that could force flight cancellations across the North Atlantic, the busiest international travel market.

Air France, Deutsche Lufthansa AG, EasyJet Plc and Delta Air Lines Inc. are among carriers watching the Bardarbunga volcano. Iceland’s Civil Protection Agency has recorded about 800 earthquakes in the area since early yesterday and raised the risk of an eruption to “orange,” the second-highest level.

The seismic activity raised concern that airlines may face a repeat of the 2010 disruptions when a cloud belched from the Eyjafjallajokull volcano forced carriers to erase more than 100,000 flights and caused about $1.7 billion in lost revenue. Ash represents a menace to jetliners because the glass-like particles can stop turbines by melting and congealing.

Airline traffic in Northern Europe would be disrupted “if the winds, as we’re seeing them today, continue” in a Bardarbunga eruption, said Melissa Anne Pfeffer, atmospheric volcanologist at the Icelandic Met Office.

Eurocontrol, the region’s air traffic manager, said there is currently no impact on aviation from Bardarbunga. The volcano lies beneath Vatnajokull, Europe’s largest glacier, and last erupted in 1996.

The severity of an eruption would depend on where the magma reaches the surface, Pfeffer said. Molten rock bubbling up under the icecap would create “a more explosive eruption” than one that occurs in the open, Pfeffer said.

Awaiting Directions

“We’re in dialogue with authorities awaiting their directions in case of eruption,” Trine Kromann-Mikkelsen, a spokeswoman for Sweden’s SAS AB, said by e-mail. “We are always prepared for irregularity and have experience from last time.”

The aviation industry has developed better tools to monitor volcanic clouds since the Eyjafjallajokull eruption, according to a statement from Eurocontrol.

“Europe is more prepared to deal with volcanic ash these days; we have better mechanisms in place than we did in 2010,” Eurocontrol said.

The Eyjafjallajokull incident prompted European officials to close the majority of airspace in the region for six days, stranding 10 million passengers. There was less disruption to travel from a 2011 eruption, which was smaller and only affected airports in Iceland and northern Germany for a few hours.

EasyJet, a Luton, England-based budget carrier, said that in the event of an Bardarbunga eruption, it plans to work with partners including Icelandic officials, planemaker Airbus Group NV, Nicarnica Aviation, which developed technology to detect airborne volanic ash, and FutureVolc, a 26-partner consortium funded by the European Commission.

The team will “ensure that ash from it is detected and charted from space, using infrared cameras on European weather satellites or through the potential airborne deployment AVOID technology,” EasyJet said in an e-mailed statement.

–With assistance from Andrea Rothman in Toulouse and Thomas Black and Mary Schlangenstein in Dallas.

To contact the reporters on this story: Julie Johnsson in Chicago at jjohnsson@bloomberg.net; Omar R. Valdimarsson in Reykjavik at valdimarsson@bloomberg.net; Kari Lundgren in London at klundgren2@bloomberg.net. To contact the editors responsible for this story: Ed Dufner at edufner@bloomberg.net; Benedikt Kammel at bkammel@bloomberg.net.