Currently there are four BWB designs that have been tested in the LST-1 wind tunnel at Flight Technology and Test Centre (FTTC), UiTM since 2005. The objective of this paper is to analyse their flight performance of these four BWB UAVs in terms of airspeed flight envelope, endurance, range and rate of climb as a function of the number of batteries and to determine the optimal number of batteries to be carried for 1-hour endurance mission and 3-hour endurance mission. The targeted cruising-loitering airspeed mission for all these BWBS are around 20 to 40 mph (8.9 m/s to 17.8 m/s) and they are to possess the lowest take off/landing speed and the highest maximum speed possible. This paper also seeks to find the best design of the four to explore its maximum potential in the near future where a prototype will be constructed. Unlike conventionally powered aircraft that uses fuel, which burns out thus reducing total weight of aircraft as it flies for long hours, these four BWB electric-powered vehicles carry batteries and the weight shall remain constant throughout the flight.