The Helios Prototype is a remotely-piloted solarpowered flying wing developed to demonstrate the capability of achieving two significant milestones for NASA's Environmental Research Aircraft and Sensor Technology (ERAST) project.

Firstly, reaching and sustaining flight at an altitude near 100,000 feet and secondly, flying non-stop for at least 24 hours including at least 14 hours above 50,000 feet.

In 2001, Helios achieved the first of these goals by reaching an unofficial world-record altitude for a non-rocket powered aircraft of 96,863 feet and sustaining flight above 96,000 feet for more than 40 minutes during a test flight near Hawaii.

The Helios Prototype is an enlarged version of the Centurion flying wing, flown at Dryden, California in late 1998 to verify the handling qualities and performance of a lightweight all-wing aircraft of more than 60-metre wingspan.

It was renamed the Helios Prototype to clearly identify it as a forerunner of the eventual Helios production aircraft, which will be designed to fly continuously for up to six months at a time on scientific and commercial missions.

Developed by AeroVironment Inc, of Monrovia, California, the Helios Prototype has what is probably the most interesting pedigree in aviation history. In 1959 the British industrialist Henry Kremer announced a competition with a prize of $95,000 for the first man-powered aircraft to successfully demonstrate sustained, manoeuvrable human-powered flight.

Dr Paul MacCready and Dr Peter Lissamen designed the "Gossamer Condor", constructed of thin aluminium tubes and Mylar film, supported with stainless steel wire. On August 23, 1977, championship bicyclist and hang-glider enthusiast Bryan Allen flew the Condor for 7 minutes, 2.7 seconds, over a closed figure-8 course to win the coveted $95,000 Kremer Prize.