The storm has caused minor disruptions for U.S. airlines. Delta said it altered routes for "a handful" of flights and that changes are adding about 15 minutes to travel times.

"We are undergoing a series of solar bursts in the sky that are impacting the northern side of the world," said Delta spokesman Anthony Black on Tuesday.

"It can impact your ability to communicate," he said. "So, basically, the polar routes are being flown further south than normal."

United Airlines (UAL.N) spokesman Mike Trevino said the carrier diverted one flight on Monday because of the storm, but none on Tuesday.

American Airlines (AAMRQ.PK) spokesman Ed Martelle said the airline has no operational impact due to solar flares but that it is monitoring the atmosphere.

The National Oceanic and Atmospheric Administration said in a press release on Monday that it had issued a watch on Sunday for "a geomagnetic storm associated with a bright flare on the sun."

NOAA said it also issued a warning for solar radiation storming, which can affect communications systems at high latitudes, satellites in space and rocket launches. NOAA said it was the strongest solar radiation storm since 2005.

(Reporting By Kyle Peterson; Editing by Phil Berlowitz)

• A Permanent Economic Emergency