Two airport constraints shape every schedule: how many movements an airport can handle per hour, and when it sleeps.
Hourly capacity: every world#
Each airport declares a movement capacity per hour. When you save a schedule, your departures and arrivals are counted together with every other airline's in each hour bucket; an over-full bucket fails the slots gate (see Scheduling gates). The airport page shows this as a heatmap (movements per hour across the week, green when quiet, amber from 60% of capacity, red at or over the line) so you can spot the free hours before the wizard tells you no.
Curfews#
Some airports close at night. A curfew is a local-time window (it may wrap past midnight) during which neither departures nor arrivals are allowed; the gate checks your departure at the origin and your arrival at the destination. Airports without one show as 24h on the Stations page. On the map, the Night layer draws an amber ring around each airport currently inside its curfew, useful for eyeballing long-haul arrival times.
Slot-ledger worlds: slots as property#
Some worlds enable a full slot ownership ledger (a world-creation choice; check yours). There, capacity is divided into 15-minute buckets, and each bucket's arrival and departure movements are property:
- Holdings are acquired automatically, first-come, when a schedule commits; there is no separate purchase step for pool slots.
- You keep holdings through schedule edits, but the season is use-it-or-lose-it: at each rollover (by default every 180 days; your world may differ) holdings shrink to what you actually scheduled. The Slots page flags unflown holdings as at risk and shows the next rollover date.
- Each bucket also has directional caps: arrivals and departures are separately capped at a fraction of the bucket total, deliberately overlapping so the mix can flex.
- When a bucket you need is dry, the failure reads like a coordinator's letter: how many you need, hold, and remain in the pool, plus the nearest bucket with room within two hours.
The secondary market#
Unused holdings can be sold airline-to-airline. From your Slots portfolio, list a slot with an ask price; other airlines' listings appear on the same page and can be bought outright. A congested hub's peak-hour buckets are scarce, permanent assets; early movers at a growing airport end up owning the morning.
The airport page's ownership panel shows who holds each bucket at any airport, so you can see exactly which rival is sitting on the times you want, and who might sell.