Finding the Air a Bit Thin:

The high-flying RQ-4 Global Hawk unmanned aerial vehicle has suffered some growing pains—namely a couple of engine shutdowns. The events went largely unnoticed, though, perhaps because the unmanned aerial vehicle, which was sent to war while still in development, has performed so successfully. Engine maker Rolls Royce calls each of the two flameouts—one at Edwards AFB, Calif., and one in Southwest Asia—an “anomaly” rising out of the UAV’s operating environment—65,000 feet up and for up to 35 hours per mission. Dennis Jarvi of Rolls Royce told reporters in Washington, “There are many things that happen when the air gets very thin up there.” Jarvi said the company is a few weeks away from getting a “definitive answer.” In the meantime, he said, program officials have updated the engine-related software. Jarvi added, Rolls-Royce is being “conservative” about premature speculation.