Seoul (CNN)NASA prepares its half-a-century old jetliner for take-off in an airbase in South Korea.
Thirty-four scientists teamed up in this Douglas DC-8 for a mission to measure the main pollutants in the air over South Korea, for clues as to what and who is causing it.
Equipped with 25 state-of-the-art instruments, the highly-modified plane allows scientists to collect samples and data.
The flying science laboratory flew through the length and breadth of South Korea for eight hours in May, taking samples and readings.
South Korea's air quality is ranked 173 out of 180 countries, according to a recent study by Yale University. More than half the country's population is exposed to unsafe levels of fine particulate matters, the study found.
South Korea has long blamed China for much of the pollution. Although not conclusive, scientists say fine dust particles, which are very detrimental to health, may often originate closer to home.
Andreas Beyersdorf, a scientist on board the flight, said most of the pollution detected during this trip was likely to come from local sources.
To collect data, the plane flew low over South Korean cities...
... from residential areas to sparsely populated mountain ranges.
The low altitudes required skillful flying from former Air Force pilots...
...as the plane circled and flew back and forth along defined routes.
Yale University's environmental studies underline that the issue of air quality is a global problem, saying more than 3.5 billion people, half of the world's population, live in nations with unsafe air.
As more than one scientist on board said, at least South Korea is acknowledging there is a problem and opening up its airspace to NASA and its expertise.