Russia threatens Asia flight paths with possible block on Siberia airspace

Russia's threat to bar European and North American airlines from Siberian airspace, the latest salvo in tit-for-tat sanctions over Ukraine, is forcing carriers to consider other Asian routes.

United Airlines and Delta Air Lines, which rank second and third in the world by traffic, said they were weighing their options after Russia formally broached the idea of a Siberia ban. United Parcel Service, the biggest package-delivery company, is also making contingency plans.

The closure of Siberian airspace would escalate tensions between Russia and the United States and its allies in Europe, which have sought to punish Russian President Vladimir Putin for backing Ukraine's separatists.

North American and European passenger and airfreight operators cross eastern Russia hundreds of times a week because it is the shortest, and cheapest, path to Asia.

"These sanctions that are being threatened back and forth are very serious," said Brian Havel, associate dean for international affairs at DePaul University in Chicago.

"This is very cold-war-like in its thinking. Aviation was bound to come on to the agenda."

The comments by United, Delta and UPS signalled that airlines were reacting to the possibility of losing their fuel-saving Siberian routes.