The fourth Boeing [NYSE:BA] 787 Dreamliner, ZA004, has been stationed in Colorado Springs, Colo., for several days for a short series of high-field-elevation tests. Earlier this month another 787 conducted touch-and-go maneuvers in Colorado Springs.

The tests, which have to be conducted at an airport with a high elevation, follow tests on the same airplane over the weekend in Mesa, Ariz., done at a low-elevation airport in hot weather.

The 787 flight test fleet, currently comprised of four airplanes, has logged more than 840 hours of flying in the last six months. Two more airplanes are expected to join the flight test fleet soon.