My youngest son was 5 weeks old when he first flew. Since I had done a lot of flying with the older one, I was not too nervous about it. However, I had made sure to get the GO from our pediatrician ahead, and I strongly advice you to talk to yours about flying. I was recommended to bring some medication with me, since it was a long flight, but since I am only a journalist and not a ped myself, I will not advice on such things. But I suggest that you ask your pediatrician if there are any medications he would suggest you bring with you on the travel. Especially if you are planning to stay away for awhile.
Also, check with your airline which regulations are in effect when it comes to fluid (yes, medicine in fluid counts). Sometimes they want you to have a prescription printed on the bottle, to make sure it is for you or your kid.