The official Pokémon website has announced that Aerodactyl will be distributed to all Pokémon World Championship 2019 attendees in Washington, DC, United States.

Get the Fossil Pokémon Aerodactyl at Worlds

Get Aerodactyl in Washington, DC, this August at the 2019 Pokémon World Championships! All Pokémon World Championship attendees can get a special Aerodactyl with held item Rare Bone.

If you're attending the Pokémon World Championships on August 16 to 18 and want to add this special Aerodactyl to your Pokémon collection, remember to bring your system in the Nintendo 3DS family and your Pokémon Ultra Sun, Pokémon Ultra Moon, Pokémon Sun, or Pokémon Moon game. You can get only one Aerodactyl per game. Aerodactyl will be available outside of the main event hall, so you don't need a Worlds entry badge to receive the Pokémon.

Look for signs at the Pokémon World Championships for distribution times and instructions on how to get Aerodactyl.

Source: https://www.pokemon.com/us/play-pokemon/worlds/2019/pokemon-distribution/