After the planned merger, the newly-formed company will replace the NASDAQ OMX Group, Inc. (NASDAQ:NDAQ) as the second largest stock exchange operator in the country by volume after NYSE Euronext (NYSE:NYX). Currently, Direct Edge occupies third spot while BATS is the fourth largest exchange operator based on trading volume. Both of them favor high speed electronic trading. The announcement comes only a few days after NASDAQ halted trading due to technical problems.