FAA Federal Aviation Regulations (FARS, 14 CFR)

The administrative law judge shall issue an initial decision or shall rule in a party's favor only if the decision or ruling is supported by, and in accordance with, the reliable, probative, and substantial evidence contained in the record. In order to prevail, the party with the burden of proof shall prove the party's case or defense by a preponderance of reliable, probative, and substantial evidence.