Nothing really, so far as we can see.
So one has to wonder why there is so little travel advertising in the Sunday Travel section. Sometimes, there only one or two ads in there. It's a national run - they don't do regional editions - and the open rate is a shade less than $1,200 per column inch. That means for about $18,000 you can run a 3 x 5 ad with almost no competition. Nationwide.
Which is to say, to people all over the country who are enjoying the Sunday Times over breakfast and coffee. And, because they are reading the Travel section, they have an interest in travel. These folks probably also have the time and money to travel, which makes that 18 grand a pretty good deal.
A highly visible 3 x 5 ad one time in a respected newspaper with a desirable readership. Well, no, it's not exactly a collection of cubes and leaderboards that come and go on all sort of websites (including some you'd never want to visit), and it's not the same as Adwords.
But it can sure as hell make those other things work harder.