Heathrow Logic fails when Actual and Scheduled dates differ.

[FergM]

The heathrow logic uses scheduled date to guess the actual (arrival or departure) date

• This fails for example if a flight is scheduled at 23:50 but departs at 00:05 the next day.
  • In such a case the actual date will be guessed wrong
  • The delay_mins will look like the flight departed nearly 24 hours before scheduled.
• This is detailed at the end of notebooks/NB04 - Heathrow Analysis.ipynb