PALMDALE, Calif. — Tucked away here in the Mojave Desert, the assembly plant for the high-flying Global Hawk jet resembles a giant hobby shop.

Work tables surround a handful of fuselages, and an unusually long wing — needed to slip through the thin air at 60,000 feet — is ready to be bolted into place. Open panels await controls for cameras and eavesdropping gear, and bright blue tool bins and parts vats are scattered around the concrete floor.

Just 50 people work in the factory and a test hangar, and only five of the drones will be built this year. But despite a spate of delays, second-guessing and cost overruns, the Global Hawk is once again on track to replace one of America’s most noted aircraft: the U-2 spy plane, famed for its role in the cold war and more recently Afghanistan.

The Air Force decided last month to stick with its $12 billion Global Hawk program, betting that the unmanned drone can replicate the aging U-2’s ability to sweep up a broad mix of intelligence from commanding heights, and do it more safely and for much longer stretches than the piloted U-2. The Navy is also onboard, with plans to spend $11 billion on a version that could patrol vast ocean areas.