We used a polar cooler last month and not a thing even began to dethaw. That included a 7lbs Angus tenderloin which took an additional 2 days to finish the thawing process after we arrived.

Froze the the meat, fish, etc... for a couple weeks before the trip. Loaded the cooler 36 hours before the trip and put the whole thing in the freezer. The neat thing about a polar cooler is it will fit under the seat.

Highly recommend you do a search on Polar Cooler. They are well made and really do work.