Deal with gaps in ADS-B data for international flights

Air New Zealand flight 6 returns some strange behavior, perhaps because coverage gaps or anomalies aren't dealt with properly. 

<img width="3955" height="2217" alt="Image" src="https://github.com/user-attachments/assets/af65412c-8d46-4c42-8a3b-cff945170959" />

The command: 

```bash
pyfr24 smart-export --flight NZ6 --date 2025-08-02 --timezone "America/New_York" --background esri-satellite
```