Like above, I have been 24 hours with Polar Bear cooler (24 can size) fully packed with frozen items and stayed frozen . A few items with minimal thawing.

I have done 2 pounds Dry Ice , same cooler /items and at 24 hours solid frozen. I am sure it would have been fine with 36 hours. Flying, each passenger, can have up to 5 pounds.... so 5 pounds MAX in a single cooler. I would not do more than 2-3 pounds in this size cooler.