Via Engineering and Technology Magazine:
Due to the size of aircraft, and the very high number of tasks that need to be executed on a limited number of units, the use of specialised fixed-base robots, like those already in use by the automotive industry, is impossible in the aeronautical industry.
Using humanoid robots allow much greater versatility than their stationary counterparts with their ability to enter confined spaces and traverse stairs and ladders that are typically designed for human use.
The Joint Robotics Laboratory has already developed humanoid robots, called HRP-2 and HRP-4, that it will use as a platform to test newly researched capabilities. They are slightly shorter than an average human and about half the weight.