That is a strange one.

It seems that content.onlineagency are themselves a travel company (http://content.onlineagency.com/c/74/74684/7466411_74684.htm)

It's strange that they have that page that is clearly copied.

I can't see any connection between the 2  companies, apart from their websites are quite similar in terms of quality.

The only thing that I can think is they are actually competitors and somebody is trying some sort of negative SEO tactics.

But this shouldn't really effect your clients site, just disavow and move on is my advice