(Reuters) - Spirit Airlines Inc (>> Spirit Airlines Incorporated) baggage handlers have voted to be represented by the machinists union, joining three other employee groups at the low-cost carrier that have bargaining agents.

Of 217 eligible voters, 131 voted to join the International Association of Machinists and Aerospace Workers, according to certified results from the U.S. National Mediation Board, which supervised the election that began June 16 and ended on Tuesday. Thirty-two of the Spirit Airlines workers voted for no representation.

"While we are disappointed by the results, we fully support our Team Members' right to choose and moving forward we are committed to working with" the machinists union, Spirit Airlines spokesman Paul Berry said in a statement.

The ramp employees work at airports in Fort Lauderdale, Florida; Detroit; Atlantic City, New Jersey; and Myrtle Beach, South Carolina, the machinists union said.

"The days of Spirit management unilaterally dictating wages and working conditions end today," Daniel Krampert, a Spirit ramp agent in Atlantic City, said in a statement provided by the machinists.

The Spirit Airlines election comes as unions mount a push to make new inroads at U.S. carriers, particularly low-cost airlines. Pilots at JetBlue Airways (>> JetBlue Airways Corporation) voted to join the Air Line Pilots Association in April, the first successful union drive by a worker group at that carrier. Union organizing drives are also under way at carriers such as Virgin America, the U.S. carrier in which Richard Branson's Virgin Group has a minority stake.

The machinists union has a flight attendant campaign under way at Delta Air Lines (>> Delta Air Lines, Inc.), spokesman James Carlson said.

Spirit, based in Miramar, Florida, offers low airfares but charges fees for many other optional services. The carrier had just over 3,600 workers at the end of 2013, 59 percent of which were represented by labor unions. Its pilots are members of the Air Line Pilots Association, and flight attendants and dispatchers are represented by the Association of Flight Attendants-CWA and the Transport Workers Union, respectively.

Spirit said in its most recent annual report that labor expenses represented about 19 percent of its operating costs in 2013.

Shares of Spirit Airlines fell 1.5 percent to $62.41.

(Reporting by Karen Jacobs in Atlanta; Editing by Mohammad Zargham and Jonathan Oatis)