 Lockheed Martin has been promoting a UAV version of the U-3 designated the "U-2U" as an alternative to the Global Hawk, though so far with little success in the face of current Air Force commitments.Northrop Grumman is now building the "Block 20" or "RQ-4B" Global Hawk.This variant features an uprated engine; a wingspan stretch from 35.4 meters (116 ft) to 39.9 meters (130.9 ft); and a fuselage stretch from 13.5 meters (44 ft) to up to 14.5 meters (47.6 ft).