Oliver Jeffers sketchbook illustrations for the United Airlines in-flight magazine. It looks like they were drawn a pocket-sized Moleskine Cahier using waxy colored pencils and some white ink or gel pens. Gorgeous!
I made a bunch of maps for the United Airlines inflight magazine. They are all geographically accurate.
Visit Oliver Jeffers site to see all the images from the collection and admire his other work as well. Check out the sketchbook section to see some amazing collages and messy, well-loved sketchbooks.
(shoutout to The Cramped for the tip)