United Airlines Inc. defeated an appeal in a discrimination suit by an employee who said he suffered from an attention disorder and was fired after he failed a drug test.

Michael Fragada didn’t offer enough proof to go to trial on his claims for disability discrimination under the California Fair Employment and Housing Act, the U.S. Court of Appeals for the Ninth Circuit said in an unpublished opinion.

Fragada, a ramp serviceman, said he was discriminated against because he suffered...