WASHINGTON — Mr. Smith’s identity was shielded by a six-foot high folding wall. His voice was electronically muffled, making him sound like that robot from the 1960s TV series “Lost in Space.”

Like the robot’s infamous line — “Danger, Will Robinson” Mr. Smith also had a warning last month: The Federal Aviation Administration does some shoddy work to ensure airline safety. Mr. Smith should know, he’s one of the FAA’s inspectors.

Maine Sen. William Cohen brought Mr. Smith, not his real name, to Washington April 30 to testify before Cohen’s subcommittee on Government Affairs. Cohen did all he could to ensure Smith would remain anonymous, including clearing the hearing room once Smith concluded his testimony so he could leave in solitude.

Now, Cohen says, the FAA might be conducting its own investigation — not into its safety standards, but in a search to determine who Mr. Smith is.

“These allegations, if proven valid, are very disturbing,” Cohen, a Republican, wrote to Attorney General Janet Reno in requesting a Justice Department investigation.

The FAA denies any wrongdoing and says there is no search into Mr. Smith’s identity. “The FAA has no knowledge of that,” said spokesman Hank Price.

But in the days and weeks following the hearing, Cohen’s staff received numerous phone calls from other FAA employees. Some called to provide more details of FAA blunders, others called to warn the senator of a possible witch hunt.

“The employees informed the subcommittee that the FAA is reviewing time and attendance records for the date of the hearing and, even more alarming, is using some form of computer techniques to unscramble the voice of the witness,” Cohen wrote to Reno.

In his testimony at the hearing, Mr. Smith said the FAA does not provide adequate training for inspectors, many of whom learn only on small planes but are now examining jets. Mr. Smith himself was assigned to inspect an aircraft of which he didn’t know how to open the door.

He also said the FAA spent far too much time on paperwork. “The wings could be falling off, but as long as the paperwork’s OK, that’s all the FAA was concerned about,” he said.