Though I'd never heard about it before moving to Switzerland, EasyJet is the Southwest Airlines of Europe.
Every few months they'll advertise a group of popular fares - usually on billboards around the city. The posters aren't award-winning, breakthrough creative, but I do think they're very good. Most airlines (as with most car companies and retail stores) seem to abandon any sense of brand-building when they have a price to push. But EasyJet consistently does a nice job of ticking both boxes. No one would ever confuse an EasyJet ad for a RyanAir or Baboo promotion.
Some visuals are much better than others. (I like the rugby-Toulouse connection, but King Tut for a flight to Egypt? D for effort.) But they're always a mental connect the dots for the viewer. And as someone once told me, what happens in the mind stays in the mind.