(Credit: Patent Yogi/YouTube) Limited flight times are such a drag — and Boeing seems to agree. The company just received a patent for its design for a drone that can remain airborne in perpetuity. Flight times are constrained by the amount of energy or fuel a drone can store on board. But Boeing plans to circumvent this limitation with a retractable tether that latches onto ground-based power sources without requiring the craft to land. The patent was filed in 2013, and the U.S. Patent and Trademark Office just approved the company’s application earlier this week.