It used to be that a trip to Europe was a relatively quick affair: a ride to the airport, a zig-zag through security, a longish flight across the Pond, and a connection to a waiting friend, taxi, or rail stop to whisk you to your destination. That was before volcanic activity in Iceland sent clouds of ash billowing into the skies so high that flights have been grounded as far away as Italy several days after the eruption (via The Associated Press). Though the ominous yet spectacular plumes of ash aren't visible in Colorado, a domino effect has stranded some passengers here, too, while other flights head toward a gray horizon. German aviation officials cleared Lufthansa Airlines to fly from Denver to Frankfurt last night, writes 7News. A corporate spokeswoman says pilots have shown that planes could be navigated at lower altitudes, apparently under the dangerous ash, which can clog giant engines and leave a gunky mess on windscreens. British Airways flights will apparently resume Wednesday evening, notes the Denver Business Journal. Airlines, many struggling financially, are taking a heavy hit because of the hazard. United Airlines, for example, is losing as much as $8.4 million a day in revenue, according to analysis cited by the Journal. Countless Colorado residents are stranded abroad, including dozens from Boulder and Broomfield counties, points out the Daily Camera. Among them is Matt Walker, a 21-year-old University of Colorado student, who says he's not too upset about being stranded in a ski resort in Sweden. "We are passing the time by going skiing in the public park here during sunny days, then partying at night," he says. "Lots of hot girls, too, and we luckily have Internet, so we can watch movies and use Facebook." Walker is bummed, however, that he will miss CU's 4/20 marijuana celebration later today, where thousands of students are expected to express their support for legalizing marijuana via smokeout. Although the school ranks number five in the nation for marijuana use, The Daily Beast puts Boulder at number 19 on its list of America's 40 Highest Cities. Denver, which doesn't make the Beast's curious cut, is holding its own International Cannabis Day rally today at Civic Center Park. Westword's Patricia Calhoun has details.