Roadrunner Transportation Systems Inc. continued its acquisition spree by announcing it bought Active Aero Group, a provider of air and ground expedited transport services, for $115 million in cash.

The acquisition marks Cudahy, Wis.-based Roadrunner's fourth so far this year, and further broadens the company's offerings beyond its traditional long-haul, less-than-truckload (LTL) service. Roadrunner's three prior acquisitions allowed it to gain footholds in the international logistics, U.S.-Mexico, and warehousing markets.

Based in Belleville, Mich., Active Aero mostly operates in the United States and has a smaller operation in Mexico. It owns 10 all-cargo aircraft and operates 50 trucks that are mostly owned by independent contractors. Active Aero generated about $265 million in revenue during the 12-month period ending June 30. The transaction is expected to close by the end of Roadrunner's third quarter on Sept. 30.

"The ability to provide air and ground expedited services to meet customers' total transportation needs has been a key strategic objective for Roadrunner," said Mark DiBlasi, Roadrunner's president and CEO, in a statement.

DiBlasi had telegraphed to the market early this year that Roadrunner would be acquisitive throughout 2014.