What is the policy on powders? Are they allowed?

Starting June 30, 2018, if you are traveling from an international last-point-of-departure to the U.S., powder-based substances in carry-on baggage greater than 350mL or 12 oz. may require additional screening at the central checkpoint. Powder-like substances over 12 oz. or 350mL in carry-on that cannot be resolved at the central checkpoint will not be allowed onto the cabin of the aircraft and will be disposed of.  

For your convenience, place powders in your checked bag.

The measures have already been implemented at U.S. airports nationwide to identify and prevent potentially dangerous items from being brought aboard the aircraft. There are no changes to what is allowed in carry-on baggage at U.S. airport checkpoints.