These bundles of keywords are generally pretty imprecise and likely based on some of the AdSense lexicon clusters. Undoubtedly a few erroneous words, timed with something like a Coke promo or book launch or whatever would cause this kind of bump.

For example, if there was an author named John Lufthansa launching a book, that would likely also trigger a jump in the air travel trends, erroneously, as users search for just the last name.