This has become an issue for photographers worldwide. Now the Federal Aviation Administration (FAA) has new regulations for how you must carry them when you fly. Don’t pack spare lithium-ion batteries in checked baggage, as they: “present a risk of igniting and fuelling fires in cargo/baggage compartments”.
You must carry them with you and pack them in your carry-on. Terminals must be packed so as not to come into contact with other metal objects. The new rules stipulate the Watt-hour capacity of batteries you may carry. The guidelines are currently limited to US-based airlines and flights that depart and land at US airports but it’s likely to extend to other countries. So check with your airline at time of booking and ask what their policy is so your next trip is not ruined by you not following their rules.