A flight number saves only if every one of seven gates passes. The schedule wizard runs them live as you type: each edit is checked against the real engine and the checklist shows pass, fail or pending per gate, with the exact reason on failure. Nothing is ever half-saved: fix the red lines or nothing happens.
| Gate | What it checks | Typical rejection |
|---|---|---|
| Traffic rights | Your nationality may legally fly each leg | Cabotage inside a foreign country; both endpoints foreign with no treaty |
| Range | Each leg is within the aircraft's ferry range | Sector longer than the type can fly at all |
| Runway | Both airports' runways fit the type | Runway shorter than the type's requirement |
| Slots | Hourly movements at each airport fit capacity | An hour bucket already full across all airlines |
| Curfew | Departure and arrival local times avoid night closures | 23:40 arrival into a 23:00–06:00 curfew |
| Rotation | The tail's whole week chains cleanly | Turnaround too short; aircraft ends up at the wrong airport |
| Maintenance window | Enough qualifying ground time each week | Rotation too dense to maintain the aircraft |
The gates in detail#
Traffic rights is the hard regulatory gate and is checked first; if it fails, the rest are not evaluated. Domestic legs are yours only in your home country (or inside a bloc that grants cabotage). Legs touching your home country are default-granted in most worlds; hard-mode worlds are restrictive. A leg between two foreign countries needs a fifth-freedom treaty and a rotation anchored at home. See Stations for why your home matters.
Range has a softer edge than it looks: beyond the type's full-payload range a sector still flies with restricted payload (the wizard shows the percentage of seats you can actually sell), and only beyond ferry range is it impossible.
Slots counts every movement (yours and everyone else's) per airport per hour against the airport's declared capacity. Worlds with a slot ledger add a second, stricter test based on slot ownership per 15-minute bucket, with a counter-offer of the nearest free time when a bucket is dry; see Slots & curfews.
Curfew checks departures at the origin and arrivals at the destination, in local time, including windows that wrap past midnight.
Rotation treats the tail's full week as one closed tour: each flight must depart where the previous one arrived, with at least the type's minimum turnaround between them, and a newly-assigned rotation must pass through the airport where the aircraft is parked.
Maintenance window demands qualifying ground stops, each at least 2 hours long by default, adding up to 12 hours per week by default (your world may differ). One long overnight stop or several shorter ones both work, at any airport.
Unassigned numbers#
A number created without an aircraft ("in the pool") is only checked against traffic rights and departure curfews at creation. The equipment gates (range, runway, slots, arrival curfews, rotation and maintenance) run when you assign it to a tail. Round-trip pairs are validated as a single unit throughout, because one direction alone can never close a weekly tour; see Flight numbers & pairs.