STATEN ISLAND, N.Y. — After nearly 50 years in the school transportation business, Atlantic Express Transportation Corp. is set to close down at the end of the year.

On Wednesday, unionized drivers with Local 1181-1061, Amalgamated Transit Union, voted down a new contract offer from Atlantic Express.

“We are very disappointed with the outcome of the union vote,” Atlantic Express officials said in a statement. “Our goal was twofold: to enable Atlantic Express to continue our operations in a competitive and financially stable structure to ensure we continued our leadership in the school bus industry while preserving jobs and our company.”

With a fleet of more than 5,000 school buses, Atlantic Express is the fourth-largest contractor in North America. The company, founded in 1964, has operations in New York, Massachusetts, California and Pennsylvania.

In early November, Atlantic Express announced that it had filed for bankruptcy, citing its union battle, bidding issues and challenging earnings as key factors. Officials said at the time that the company would use the Chapter 11 process to explore the availability of additional debt or equity financing, market its assets for sale, and continue what they described as “challenging labor negotiations” for a new collective bargaining agreement with Local 1181.

On Wednesday, with the union having voted down a new contract, Atlantic Express officials said that they “gave the union our best offer, which was significantly better than what the new companies in the industry are providing. Without this labor contract, we have no choice left but to proceed with the sale of all of the company’s assets and contracts.”

Atlantic Express officials added in their statement that the company “has had the great privilege and honor of serving many great school districts, municipalities and regions for over four decades. As we begin the process of closing our business, we will work closely with all of our customers on contingency plans to ensure as smooth a transition as possible for everyone concerned.”