Flew with my Mavic over the summer. Brought 3 batteries total, installed one and carried the other two in LiPo bag. Also used 3M blue tape to cover the terminals. The LiPo protection bag wasn't necessary in my case, but I figured if the battery did decide to go into runaway at least I could say that I attempted to go above the minimum requirement.
Check with the airline's web page, most have some sort of FAQ that addresses LiPo batteries.
From the Frontier (airline I flew) FAQ:
Carry-On: Yes; however, a limit of two loose lithium batteries may be transported when stored in zip top plastic bags, original retail packing, or when the terminals are protected with non- conductive tape or when installed within electronic devices.
Lithium-ion batteries, weighing 8 grams or less per battery.
Lithium metal batteries, weighing 2 grams or less per battery, may be accepted.
Mavic batteries are within those limits. I'm pretty sure this is the same as the TSA recommendation, but remember that the airline has the final say, not the TSA.