Growing up in the 1960s had a number of very cool moments.
I grew up in Yorkville area of Toronto, the "Hippie" capital of Canada (It was our Haight/Asbury) and spent the majority of my summers on the Jersey shore in Ocean City where "skywriting" was a daily method of selling all-you-can-eat buffets and local resturants. In Toronto it was the annual CNE - "The Ex".
So today, it seems it's back. And it's new. These new "skywriters" can fly in 5 or 6's and spell out just about anything.
A band like Phish with legions of loyal followers doesn't need advertising. But they have it anyway... very cool skywriting is so 1960s... remember trends get reborn everyday.