Final answer:
The contract between Juliet and Romeo was formed when Romeo accepted Juliet's offer, with the airplane to be delivered in the future.
Step-by-step explanation:
The contract between Juliet and Romeo is formed at the point when Romeo accepts Juliet's offer to buy his airplane. In legal terms, a contract is typically formed when an offer by one party is followed by an acceptance from the other party. In this scenario, Juliet's offer constituted the first step to creating a contract.
When Romeo communicated his acceptance of the offer, regardless of the future date agreed for delivery of the airplane, a legally binding contract came into existence at that moment of acceptance.