Seafair can mean only one thing: the Blue Angels are back in town and they have been roaring over the city all week during practice.
The contrast is delicious: as a city we're proud to have recently-passed plastic bag ban (which is a good move) and yet today we'll all gather and watch a fleet of F/A-18s each burn some 1300 gallons of jet fuel for the show along.
(I know that plastic bags are largely made from ethylene, derived from natural gas, and the petroleum by-product used in the process, naphtha, would probably just be flared off otherwise, but still, the ban is more about changing habits to cut down on wanton excess and wasteful habits.)
Bonus fact: Over the course of a year, the Blue Angels use 3.1 million gallons of fuel for transportation, training, shows, etc. Wow.