Scientists report that another volcano in Iceland could erupt soon, leading to widespread delays and groundings of airline flights across Europe.

In preparation of a worst-case scenario, airlines have raised their volcano alert status to orange, the second highest level threat, meaning that an eruption is possible, but not imminent. Red signifies imminent eruption and travel delays.

Scientists have kept an eye on the volcano, Bardarbunga, Iceland's fourth most active volcano, for some time, but because it's covered completely in ice, they relied on scientific instruments to do so. Recently, a series of earthquakes and rumblings underneath the volcano indicated magma moving towards the top of the volcano's surface, which would result in eruption.

This earthquake activity started on Aug. 16, and tremors are now occurring regularly. Although area residents cannot feel these small tremors, they are still among the strongest occurring in the in the area for nearly 10 years.

"Presently there are no signs of eruption, but it cannot be excluded that the current activity will result in an explosive subglacial eruption, leading to an outburst flood (jökulhlaup) and ash emission," says the Icelandic Met Office. "The situation is monitored closely."

Regardless of how likely eruption is, there is concern in the travel industry. In 2010, the Eyjafjallajokull volcano erupted and caused a cloud of ash to rise into the air that grounded flights into and out of Europe for six days, leaving passengers stranded, and resulting in a loss revenue of $1.7 billion.

Fortunately, experts predict that if Bardarbunga erupts, the effect on air traffic would not be as dramatic, thanks to what was learned during Eyjafjallajokull's eruption.

"The clues from the pattern of earthquakes show that seismic energy is being expended in two main clusters - one to the northeast on the glacier margin, and one to the east under the ice," says Dave McGarvie, a volcanologist at the Open University in Scotland. "The good news for air travel is that both these clusters are away from the heart of the main volcano, as it's in the heart that the kind of magma is produced which leads to highly explosive eruptions that produce the abundant fine ash capable of being transported long distances through the atmosphere."

So although the travel industry is proceeding with caution, most travelers probably don't have much to worry about.

If Bardarbunga does erupt, it will be the first time since 1794.