Input and amend routes.
Stock is stored on a flight basis within sector.
  1. Each route can have multiple aeroplanes flying that route
  2. Each entry is a flight on a given day, either outbound or return
  3. Each flight has a stock id and a flight number
  4. Each flight can be given a different description
Detailed entries:-
  1. Route code [TU01]
  2. Service type [TRS=Transport]
  3. Description [Morning flight or GB Airways flight]
  4. AIR [=depart type]
  5. Depart [LGW=Gatwick]
  6. AIR [=depart type]
  7. Arrive [MIR=Monastir]
  8. Stock code [Code for this flight rotation (differs from flight no.)]
Alter fields as required.