We traveled this past July and didn’t have any problem at all. I did see on the airlines (Delta) website that if you carried a syringe you would need a letter from your doctor. We never had a problem and no one ever questioned it.  We had a great trip with our 4yo cah sw daughter and our 2 yo noncah daughter. The only trouble we had was our 2 yo daughter had trouble with pressure in her ears on take off and landing.  We took little "gifts" for them to open to keep them busy since it was a long flight. Good luck and have a safe trip!