Related Clues:

• United by treaty
• Affiliated
• Into the company
• On the ship
• On 13-Across
• Ready to go, in a way
• On the plane, e.g.
• On a ship
• In a league, say
• Using a plane, train or bus
• On, as a plane
• On the liner
• Word in many union names
• In a partnership
• Like Cuba and Venezuela, e.g.