NEW YORK (TheStreet) -- The National Mediation Board said Friday it has asked the U.S. Justice Department to review the mysterious case of thousands of fraudulent signatures on cards requesting the board to call a union election for Delta (DAL - Get Reportflight attendants.

Both the airline and the International Association of Machinists applauded the move.

"We are encouraged that this matter has been referred to the DOJ," said Joanne Smith, Delta's executive vice president and chief human resources officer. "At the time of the IAM filing in January, many flight attendants were raising questions regarding the validity of the authorization cards the IAM submitted to the NMB."

In a message to Delta flight attendants issued Friday afternoon, the union wrote that "the IAM more than anyone else wants to know who is responsible for the submission of faulty cards and what measures can be taken to ensure that this and other representation campaigns cannot be similarly disrupted in the future."

An IAM spokesman declined to comment farther. The union and its backers have previously expressed concerns about fraudulent submissions in its attempted survey of flight attendant attitudes.

Delta has about 20,000 flight attendants. The IAM said in January that it had submitted nearly 12,000 signed election request cards from the flight attendants to the NMB. The NMB's minimum requirement for calling an election is 50% of the prospective bargaining unit.

The NMB "has reason to believe that some unknown person or persons knowingly submitted authorization cards with fraudulent signatures in possible violation of federal law," wrote Mary Johnson, NMB general counsel, in a letter sent Thursday to Delta and IAM officials.

"The integrity of the NMB's election process relies on each individual employee only submitted an authorization cards that he or she personally signed and date for presentation to the NMB," Johnson wrote.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.