Delta Air Lines Inc. says a federal board has upheld results from an election that blocked a union from representing its flight attendants.

Delta said late Friday that the National Mediation Board rejected claims by the Association of Flight Attendants that the company interfered in the representation election last year.

The union criticized the ruling, saying Delta unfairly pressured flight attendants to vote against representation and, in some case, supervisors made threats against union supporters.

"This is not democracy, not in outcome nor process," the union said in a statement.

Delta said the ruling would let flight attendants from Delta and the old Northwest move ahead as a combined group. Vice president Joanne Smith said Delta would immediately begin raising pay for Northwest flight attendants to Delta's hourly rates.

Tags: Delta Air Lines, National Mediation Board, flight attendants, Northwest Airlines