NASA's Stratospheric Observatory for Infrared Astronomy—or SOFIA to its friends—is actually a laboratory with wings. And right now, it's getting its decadal inspection at the Lufthansa Technik hangar in Hamburg, Germany.
SOFIA's actually a heavily modified Boeing 747 Special Performance jetliner, that flies 39,000 to 45,000 feet in the air to record infrared spectrum that's otherwise blocked by water vapor in the Earth's atmosphere. Up there, it can study celestial objects at wavelengths that just can't be observed from ground-based observatories.
But, like any plane, it needs more maintenance than a simple Earth-based observatory. So, it sits in Germany, being tended to by science personnel from the Armstrong Flight Research Center and Lufthansa's 747 specialists. Together, they'll keep it air-worthy and scientifically accurate. (Update: as commenters have pointed out, SOFIA is actually a collaboration between NASA and the German Aerospace Center, DLR—hence the maintenance taking place in Germany.) [NASA]