This story was updated at 4:51 p.m. ET.
The ash cloud belched by an erupting volcano in Iceland may have disrupted air traffic over much of Europe, but it poses no threat to NASA's planned Monday landing of space shuttle Discovery, agency officials said.
When Discovery re-enters the Earth's atmosphere Monday morning, it will be flying over the northern Pacific Ocean on a course that will take it over much of North America before it is due to land at NASA's Kennedy Space Center in Florida at 8:58 a.m. EDT (1258 GMT).
That trajectory is well clear of the ash cloud from Iceland's Eyjafjallaj?kull volcano, which has caused the worst global air traffic disruption ever seen, except during major wars, according to press reports.
"That smoke cloud will not cause Discovery any sort of issues during its re-entry on Monday," NASA spokesperson Josh Byerly said Saturday during mission commentary.
Discovery will re-enter the Earth's atmosphere far to the east of the regions of Europe and Asia where the effects of the volcanic ash cloud have been the most severe, Byerly said. The space shuttle will begin re-entering the atmosphere at a point over the northern Pacific Ocean about 650 miles (1,046 km) south of the Aleutian Islands near Alaska, he added.
Discovery undocked from the International Space Station early Saturday and is wrapping up a 14-day mission that delivered nearly 8 tons of cargo to the orbiting laboratory. The shuttle is returning about 3 tons of trash and unneeded items back to Earth. [Photos from Discovery's April 5 launch.]
Byerly said Discovery's seven-astronaut crew and the six astronauts living aboard the International Space Station have not been able to actually see Iceland's Eyjafjallaj?kull volcano due to inclination of their orbit. Iceland is at a latitude too far north on Earth for the astronauts on Discovery and station to see it from their respective orbits, he added.
The space station typically flies in an orbit tilted about 51.6 degrees with respect to Earth's equator and at an altitude of about 220 miles (354 km).
"There is a chance that the crew on the station may have been able to get some images of the haze that is over parts of Europe," Byerly said. "But so far, the shuttle and the station crews haven't' been able to see any of the remnants of that volcano, much less the volcano itself because their orbit doesn't take them high enough to cross over that part of the world."
Several NASA satellites, however, have been monitoring the volcano's eruption and ash cloud closely to measure their intensity and effects on the environment.
In addition to creating widespread air traffic woes on Earth, the Eyjafjallaj?kull volcano's ash cloud has led to some spectacular sunsets in parts of the world.
Scientists have said the eruption is still too small to have a significant impact on Earth's climate, but could have a larger effect if the eruptions in Iceland continue or get bigger.
Meanwhile, Discovery and its crew are preparing for a Monday landing to wrap up what has been a busy space mission complicated by antenna malfunctions and sticky bolts and valves of all sizes.
When the astronauts re-enter the atmosphere Monday morning, they will be flying what has become a rare flight profile over much of North America and the United States in what NASA flight controllers call a "descending node" profile. NASA has tended to avoid flying over land as much as possible since the 2003 Columbia accident, which spread debris over much of Texas and surrounding regions when that shuttle broke apart during re-entry due to heat shield damage.
Discovery's heat shield, however, is in tip-top shape and engineers cleared the shuttle Saturday for its upcoming re-entry and landing.
Byerly said early-bird skywatchers in North America will get a treat if they rise in the morning to try to glimpse Discovery's plasma trail across the sky during its Monday re-entry.
"It is a once in a lifetime opportunity," Byerly said.
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SPACE.com is providing complete coverage of Discovery's STS-131 mission to the International Space Station with Managing Editor Tariq Malik and Staff Writer Clara Moskowitz based in New York. Click here for shuttle mission updates and a link to NASA TV.