The rise in air travel has boosted online travel e-commerce spending to $103bn in 2012, up 9% compared to the year before.

According to a comScore report, air travel rose 10% during 2012 and was responsible for about two-thirds of all travel spending in the US.

comScore Marketing Solutions for Retail and Travel VP, John Mangano, said that travel has been a leading online commerce category, and despite being a pioneer in the sector 15 years ago, it is still growing at double-digit growth rates and remains very competitive.

"With the online channel driving such a high percentage of dollars within the broader travel industry, understanding the competitive landscape is essential to determining the most effective sales and marketing strategies," Mangano said.

During 2012, the website of Southwest Airlines topped the list with 20% of category page views, followed by Delta Airlines with 15.5%United Airlines at 14.7%, American Airlines at 13.2% and US Airways stood at 3.4%.

Expedia topped the list of the Online Travel Agents with 31.6% of all category page views, while Marriott led the Hotels & Resorts category with 11.7% of page views, the report revealed.

"Interestingly, not all sites are equally effective in turning page views into transactions," Mangano added.

"In some instances we see that sites require greater engagement to get to a booking, while others serve more as a venue for comparison pricing but lose out on the sale as their visitors go to other sites to book.

"So while winning the traffic battle is an important part of customer acquisition, travel companies who optimize their strategies at other phases of the funnel are the ones who ultimately drive the greatest conversion."