You can refer to this post for some great tips:
http://www.madpsychmum.com/2014/09/travel-tips-2-nursing-on-travel.html
It is best to check with the airline that you are traveling on. What my friends did when they needed to travel is that they would opt for the check in luggage option and use a cooler bag or icebox with icepacks. Also, best to check with the hotel if there is a fridge with freezer in the room. If not, you can try to see if they could help you store the expressed breastmilk in their kitchen's freezer.