Improvements in solar cell weight and performance has enabled the development of small solar powered aircraft which operate at low altitudes. Unlike high altitude pseu-dosatellites, these aircraft must contend with significant stochastic variations in wind and solar energy. This paper examines speed scheduling for solar augmented aircraft (i.e. an aircraft equipped with solar panels and a supplementary energy source which cannot be recharged in flight). We show that solar energy can be considered as identical to vertical air motion exploited by a sailplane. This permits soaring speed to fly theory to be extended to incorporate both solar energy and atmospheric vertical motion. The use of stored energy onboard allows derivation of a speed to fly theory with an arrival time constraint, allowing the exploitation of stochastic energy during a flight plan. The speed schedule is tested in Monte Carlo simulations and shows the ability to satisfy an arrival time constraint while reducing energy consumption by approximately 2% and reducing variation in final energy state by approximately 3%. The algorithm is also tested in flight using a small uas, and shows the ability to satisfy an arrival time condition within 1%.