In the camera - no issue Out of the camera - with the orange cap on Never never loose, so that the terminals could short out each other, potentially causing a fire
In real life, although I only fly a few times a year, I've never had an issue or question about the two or three spare batteries I almost always carry in my back pack. I've been dinged on my rescue inhaler more than anything else!
Here is a link to USPS rules for lithium batteries, which assume that your package will go by air. Very similar to TSA rules. When I was involved with shipping, these are the rules I used. Kinda long and technical if you're interested.
Just have one battery, So I'm OK keeping it in the camera right? Tim
Yes on keeping in camera in case asked to turn on camera - easier that way. But maybe better advise would be to buy a back up or two... the one can & will go dead at the time you absolutely don't want it to, regardless if you think it is charged. It is a rule of the photography travel gods!!!
Flying out to see my brother in Wash. state next week, And was taking my Canon T6, what are the rules for the battery?
Thanks, Tim
WOW, 4 second search found this Size limits: Lithium metal (non-rechargeable) batteries are limited to 2 grams of lithium per battery. Lithium ion (rechargeable) batteries are limited to a rating of 100 watt hours (Wh) per battery. These limits allow for nearly all types of lithium batteries used by the average person in their electronic devices.
Just returned from Texas. No batteries in cameras. Batteries in carry on in plastic bag, devices separate depending on battery size. No problem. Check airlines policy on their website.