Personal devices installed with a lithium battery of less than 100 watt hours are permitted in carry-on and checked baggage.
Loose lithium batteries are not permitted in checked baggage on any United flight. Each spare lithium battery in carry-on baggage must be individually protected to prevent short circuits. To do this, you can place each battery in original retail packaging, place each battery in a separate plastic bag or protective pouch, or insulate the batteries by taping over exposed terminals. Spare batteries must not come in contact with metal objects, such as coins, keys or jewelry, and you should take steps to prevent crushing, puncturing, or putting pressure on the battery.
In most cases, up to two larger lithium batteries (more than 100 watt hours, but not exceeding 160 watt hours) are permitted in carry-on baggage if the terminals are properly covered or insulated.
Drones are allowed in Checked baggage, and also in carry-on baggage.