I left my milk on the plane, and it came back four days later via FedEx at 36 degrees. I was traveling with four frozen bags of breastmilk in a half-gallon Yeti vessel chilled by three ice packs and a very squirmy baby. No cooler. Just momma, baby, and four bags of frozen milk in a vessel. I’m overclocking my pumping schedule right now to build more archive. So each night after my daughter went to sleep, I had pumped and frozen an extra bag of milk. In the flux of exiting the plane with a squirming baby, I left all of it in the overhead bin.
The cleaning crew had missed the vessel in the overhead bin and so by the time we figured out where it was on a new journey from Los Angeles to Nashville. To my surprise, the team at Southwest listened to the words perishable and breastmilk and understood why this was so important to me. Operations in Nashville made sure the vessel was pulled off the plane promptly and shuffled to the lost items counter. It turns out that there is no overnight option for lost and found items even with an attentive and inspired team of people working on getting breastmilk back to you. The quickest that the milk could go out was the next morning, and the only option was 2-day mail, even when I offered to pay the difference.
In my experiments, frozen milk starts to de-thaw between 36 and 48 hours in a vessel that is in a cooler. This one wasn’t in a cooler. But when it did arrive, I was delighted to learn that the milk was still at refrigerated temp. Right at 36 degrees! There was a notable lack of thaw in the ice packs too. They were still frozen solid. Fantastic not only for the fact that I could even use that milk but also for the validation of the capability. Which made me ask a question I should have asked long ago. For shorter domestic flights, I now knew that I did not need a cooler at all.