77% of US domestic air routes are a monopoly; nine routes have at least five airlines fighting for passengers

At the beginning of the year four airlines served the 500-kilometre intra-Californian market from Los Angeles to San Jose. Virgin America’s arrival in May made it five, followed by Delta Air Lines in June making it six. Virgin America's 149-seat A320 nicknamed #nerdbird performed the inaugural flight between the two airports. The airline’s CEO, David Cush, and Sir Richard Branson posed onboard to mark the new route.

Analysis of airline schedule data reveals that within the US domestic market there are around 2,780 airport-pairs connected with scheduled services in October 2013. Of these, around 2,140 are served by just a single carrier, a further 470 see two carriers competing head-to-head, another 139 offer passengers a choice of three airlines, while on 24 routes there are four airlines competing for custom. That leaves just nine routes (airport-pairs) where five or more of America’s finest airlines compete for market share. Los Angeles-Las Vegas and Los Angeles-San Jose are the only US domestic routes with six carriers competing head-to-head. Curiously, the Los-Angeles-San Jose route leapfrogged to be joint top of this table earlier this year when Virgin America (1 May) and Delta Air Lines (10 June) became the fifth, and then sixth, airlines to serve this intra-Californian market.

Five of the nine routes involve Los Angeles, three include Denver, while New York JFK and San Francisco both appear twice. The completion of the mergers between AirTran Airways and Southwest Airlines, and American Airlines and US Airways, will have an impact on only two of these routes; Denver-Atlanta and Los Angeles-Phoenix. In fact, US Airways is noteworthy for appearing just once in these highly competitive routes, less often that Frontier Airlines, JetBlue Airways, Spirit Airlines or Virgin America.

LAX-SFO top for weekly flights

Of these nine highly competitive routes, the Los Angeles (LAX) to San Francisco (SFO) market is the busiest with 362 weekly departures (that’s over 50 each day). This is way ahead of the next busiest route, Chicago O’Hare to New York LaGuardia, which has 311 weekly departures (but only four competing airlines – American Airlines, Delta, Spirit and United Airlines), and the Los Angeles to Las Vegas route, which has 240.