A Reuters wire story says NASA is planning a test flight of the solar powered Helios UAV in July over Hawaii. The test flight will attempt to break the 80,000 ft altitude record set by an earlier NASA UAV. The goal is to develop a UAV that can cruise at 100,000 ft for months at a time. At that altitude, the air is very similar to the Martian atmosphere so one use of the Helios will be to serve as a development platform for Martian aircraft. Other uses include study of the ozone layer and replacement of spacecraft such as weather satellites. Photos of the Helios are available from the NASA Helios Photo Gallery.