A union representing NASA employees says the agency’s administrator unfairly tarnished agency employees by disparaging and misrepresenting a federal air safety project.

NASA weeks ago drew intense criticism for withholding results of the research, fearing it would upset travelers and hurt airline profits.

The International Federation of Professional and Technical Engineers represents many NASA scientists, engineers and technical employees. It disputes Michael Griffin’s criticisms of the program, in which thousands of commercial and private pilots were interviewed.

It also say Griffin’s comments to Congress at an oversight hearing in October appeared to reflect fears the pilots might report to NASA higher rates of safety problems than are recorded by Federal Aviation Administration’s own monitoring.

Agency spokesman David Mould said NASA stands by Griffin’s statements to Congress.

The development is evidence of the dispute over the merits and goals of the pilot survey, staunchly defended by experts who designed it for NASA.

The union’s investigation is at least the fourth probe since The Associated Press disclosed that NASA had closed down the project and was withholding results of the research.