Jet Blue along with all the airlines have to deal with FAA and CFR rules when it comes to carrying compressed cylinders. You can carry them in certain instances, now if you fly alot and take your gear with you, invest in a pelican case and be prepared to sort thru the CFR’S for all the proper labeling details. In addition you will need shipping papers and alot of other stuff to confirm what is in the cylinder or intended to be in the cylinders.The main thing is that the valve is protected from breaking off and becoming a compressed missile in the body of the air craft. Simple solution, carry the regs and rent the tanks..I’m not even going to get into Homeland security’s rules which have muddied the waters even more.