Dist. Ct. did not err in finding after bench trial that defendant-employer did not discriminate against plaintiff-employee on account of his age when defendant failed to promote plaintiff. While defendant selected significantly younger co-worker for said position, Dist. Ct. could properly rely on testimony of decision-maker that position required strong interpersonal skills, and that successful candidate had better interpersonal skills than plaintiff and had established track record of working well with co-workers. Plaintiff’s claim that decision-maker had improperly interviewed successful candidate without interviewing others in violation of collective bargaining agreement did not constitute evidence of age discrimination. Ct. side-stepped issue as to whether causation standard applicable to federal-sector ADEA claims under section 633a required proof that age was “but for cause” (as opposed to “motivating factor”) of employer’s adverse act.