If you want to file via Leidos within ForeFlight, then you can file up to 27 days into the future. Leidos transmits flight plans to ATC 3 hours prior to your ETD. Further, flight plans may be filed with an ETD that is as soon as 5 minutes in to the future. All flight plans may only be amended or canceled up to 30 minutes prior to the ETD.
Leidos also supports sending early filed flight plans to traffic flow management, which can offer better routing with fewer delays. Here are the parameters used by Leidos to determine when a flight plan is submitted to traffic flow management:
1. For flight plans filed at a time greater than an ETD + 17 hours, at the time of ETD + 17 hour mark, the flight plan will be submitted to traffic flow management.
2. For flight plans filed between an ETD of +3 hours and an ETD of +17 hours, then the flight plan will be submitted immediately to traffic flow management.
3. For flight plans filed with an ETD of + 3 hours or less, flight plans will simply be submitted directly to ATC.