An ELSA is an Experimental Light Sport Aircraft. It can be an airplane, weight shift control, or a powered parachute. E-LSAs are based on an S-LSA but probably built by the owner/operator, not used for instruction nor hire (after Jan 31, 2010), and maintained in an condition for safe flight by the owner/operator. Existing E-LSAs are also grandfathered fat ultralights - (heavier than 254 pounds, OR carries 2 people OR holds more than 5 gallons of gas). The Special Light Sport Aircraft (SLSA) is an aircraft built to ASTM specifications. Built by the manufacturer and test flown before you buy it. SLSAs can be used for instruction and in rental fleets. In many cases, ELSAs and SLSAs are identical aircraft, just with different paperwork. SLSAs probably hold their value longer due to more stringent maintenance requirements.