Abstract: A hat accessory which may be used as a flight training aid for creating intentional vision restriction. The hat accessory is adapted to be readily attached to common baseball-style caps. The hat accessory includes a lower bill panel with an upper bill panel bonded to the lower bill panel along an arcuate bonding band. This configuration forms an envelope or pocket for receiving the cap bill. A pair of lateral wings can be provided which are bent in a downward direction to restrict peripheral vision. The hat accessory may be used for other applications including the display of commercial, political, or other messages.