What's up with those contrails in the sky over Anchorage on Tuesday afternoon?
Probably nothing, officials say.
Contrails, short for "condensation trails," are lines of cloud produced by vapor from aircraft cruising miles above the earth.
On Tuesday afternoon, a striking display of crisscrossing contrails lit up the sky above Anchorage — and social media — leading some to speculate about ominous possibilities, including an unfolding military response the public didn't yet know about.
Nope, said Navy Chief Petty Officer Brandon Raile at the Alaskan Command at Joint Base Elmendorf-Richardson.
"Our traffic has been normal throughout the day," Raile said.
A more likely explanation is a combination of clear, cold atmospheric conditions that make contrails highly visible and commercial flights from North America to Asia taking a more northerly route than usual.
"Aircraft flying in enroute airspace fly standard routes at standard altitudes," wrote Seattle-based Federal Aviation Administration spokesman Allen Kenitzer in an email. "The weather conditions must have been such that these routes were visible today."
On Tuesday afternoon, the online live flight tracking site FlightAware showed a stack of commercial jetliners flying over the Anchorage area, and on a northwesterly path over the state.
The commercial flights were heading from airports on the West Coast of the United States and Canada to destinations in Asia.
The skies over Southcentral Alaska are heavily trafficked by commercial and cargo jets flying from North America to Asia, said Dave Schneider, a remote sensing geophysicist with the Alaska Volcano Observatory who tracks flight traffic as part of his job.
He said he wasn't sure why exactly the planes were on that route.
One possible explanation: Volcanic ash warnings had been issued after an eruption on the Kamchatka Peninsula of Russia earlier Tuesday, Schneider said.
"Planes sometimes reroute to get upwind of some projected ash cloud movement," he said.
Weather in Anchorage has also been cold and clear, ideal conditions for the clouds to form and to be visible from the ground, according to the National Weather Service.