LiPo bags are not expensive and the safest method of transporting LiPo batteries.
LiPo batteries rated between 101 and 160-watt hours (nowhere near a bagfull og DJI batteries) require airline approval before allowed on the plane. Any LiPo battery that is NOT installed securely in the RC model MUST be carried in your carry-on luggage. LiPo batteries that exceed 160-watt hours are not permitted. Batteries are not required to be discharged.
Most of the airlines I’ve flown with do not allow them in luggagebintended for the hold but are ok with hand carry on luggage.