You can bring a half gallon of breast milk on an airplane, even if the baby’s not with you.  I went on my first work-related trip of the year, leaving T and O to hang out together.  Owen worked his way through the frozen breast milk supply and even tried a little formula while I was gone.  He had a cocktail of 50% breastmilk 50% formula, which he liked just fine, although it gave him revolting-smelling poo (Travis commented that he was glad he hadn’t eaten right before he changed the diaper or he would’ve hurled. Eeeewww)   I maintained a regimen of milk pumping four times a day and had a duffel bag full of milk to tote home.  I was kinda worried about getting put on the no-fly list for brining on liquids more than 3 oz in size, but the TSA now allows breast milk sans baby to be carried on as it is a ‘medically necessary  liquid’.  Good thing, as I’m fairly attaced to my breast milk ie ‘liquid gold’ and pitching it would pain me greatly.  Pretty much every nursing woman I know feels the same way about her milk.