AA005: Support Multiple Aircraft for Searching

[Heckart]

Assigned Dev: N/A

Description: the RoutePlanner() class should be able to support multiple aircraft at once. Perhaps this feature should be implemented as a separate class with multiple aircraft members?
Priority: Medium
User Story: As a user, I want to be able to find optimal routes when I have multiple aircraft for the search area.
Acceptance Criteria: When the RoutePlanner supports multiple aircraft, it completes the unit tests in 25% fewer moves compared to when using one fewer aircraft.