A runaway weather balloon as tall as a 25-story building was drifting Saturday near Iceland, disrupting air traffic after defying pursuit by Canadian, British and U.S. military planes.
Lt. Carla McCarthy, public affairs officer at the U.S. air base at Keflavik in Iceland, said the 300-foot-high balloon was floating high above the sea a few miles west of Reykjavik, the capital.
She said the balloon was being tracked by radar so that commercial flights could be diverted as necessary.
"We're tracking it using ground radar and relaying the information to the Icelandic Civil Aviation Authority," Lt. McCarthy told Reuters.
"For as long as we maintain contact, air traffic can be rerouted. We are now exploring the options available if we lose contact."
Canadian air force officials said earlier that the unmanned helium-filled balloon had remained aloft despite attempts by jet fighters to shoot it down. Two Canadian CF-18 fighters had fired more than 1,000 rounds of cannon shells at the runaway Thursday off the coast of Newfoundland.
Benedikt Grondal, shift manager at the air traffic control center in Reykjavik, said the balloon was heading due north at a speed of 25 to 40 knots and an altitude of about 36,000 feet.
"We've needed to reroute quite a lot of aircraft," he said.
Squadron Leader Chaz Counter of Britain's Royal Air Force said two Nimrod aircraft had shadowed the balloon earlier in the day before a U.S. Orion plane took up the chase.
Britain's Civil Aviation Authority reported delays in trans-Atlantic air traffic as airliners were forced to divert from their projected flight paths.
The balloon, which if deflated would cover an area equal to five football fields, went out of control after being launched Monday near Saskatoon, Saskatchewan, to measure ozone levels.