I’ve seen various estimates of what airlines spend on average with Google to secure a booking, but Advertising Age have just got their hands on some great data showing the top Google Ad Words spenders in June 2010. In the travel sector Expedia tops the list at USD $5.95 million spent with Google in one month, followed by Hotels.com at $3.3 million.

I would really love to see which airlines are on the list, but I could only find a chart showing the top 10 across all sectors, plus some individual stats on companies outside of the top ten like Apple who paid around $1 million. With Google recently allowing European advertisers to bid on competitor trademarks, these numbers will probably only go up.

Update: I’ve noticed a serious typo, so I’ve changed the Expedia number from 3.95 to 5.95 million