United and Continental Airlines announced their plans to merge today and the combination of the two airlines will create the world’s largest carrier in terms of passenger traffic. Together United and Continental will surpass Delta with 21% of seats in the U.S. market after the acquisition of Northwest in 2008. Among US Internet visitors, the website of Southwest Airlines consistently ranks 1st by market share of visits, followed by Delta and American. Assuming a combination of visits for the websites of United and Continental, the total market share of visits would equal 11.67% and rank in third place, displacing American.

As an example of the combined traffic following a merger or acquisition, the share of visits to Delta.com increased following the redirects of traffic to nwa.com.

The combination of key markets in the US will be beneficial for both United and Continental, where each attract a significantly higher share of visits in DMAs where their hubs are located. For the 4 weeks ending April 24, 2010, the top 2 DMAs ranked by visits for Continental.com were around the Newark, NJ and Houston, TX hubs with nearly 27% of visits in the New York, NY DMA and another 10% of visits from the Houston, TX DMA. Similarly for United, the top DMAs ranked by visits were Los Angeles, CA, San Francisco, CA and Chicago, IL. The DMAs for each of the airlines complement each other well to provide strengths in major US markets with little overlap in audiences.