Lipo safe bags perse are really not a requirement, however most airlines, and I say most because some policies differ, just require electrical tape or similar covering the contacts AND for the batteries to be with your carry on luggage. It is likely to have the batteries inspected even if you don't declare them as they will be discovered during Xray. Some airlines permit a battery mounted on the craft even if it's in the luggage compartment of the aircraft. I have transported 2 types of a/c, large format (Inspire) and compact portable (EVO) Inspire in the aircraft cargo bay and EVO as carry on. Both times Security requested I take the batteries out of the bag and they inspected the power rating, both passed fine even though the larger TB48s from the Inspire are actually a bit above what is considered "safe" for the airlines. I had the Inspire checked even on re-entry to the USA by customs, but all good.