I have seen my fair share of mid-century travel posters and there are some truly amazing designs out there, but this one is probably my favorite. Every time I see it, I smile.
It's known as Rainboeing the Skies, for fairly obvious reasons, and was used to announce the addition of the Boeing 747 to El Al Israeli Airlines. It was designed by Dan Reisinger in 1971.
Reisinger did a whole series of amazing work for El Al.