What is a SID and STAR in aviation?
A SID (Standard Instrument Departure) is a published flight route from a runway to the en-route airway structure. A STAR (Standard Terminal Arrival Route) is the opposite - a published route from the en-route structure down to an airport.
Both define a sequence of waypoints with altitude and speed restrictions at each fix. Pilots follow these automatically when cleared by ATC.
Why they exist
Without published procedures, every aircraft would need individual routing instructions from the controller. SIDs and STARs let controllers say "descend via the PARCH4 arrival" instead of issuing a dozen separate altitude, heading, and speed commands. They keep traffic flowing predictably through busy airspace.
How they work
A STAR typically looks like this:
- Aircraft enters the procedure at a transition fix (where en-route traffic joins)
- Follows the common route through a series of waypoints, descending to meet altitude constraints at each
- Branches onto a runway transition for the specific landing runway
Each waypoint can have constraints:
- At - must cross at exactly this altitude (200ft tolerance)
- At or above - minimum altitude gate
- At or below - maximum altitude ceiling
- Between - must be within an altitude window
Speed restrictions work the same way. Below 10,000ft, all aircraft must stay at or below 250 knots.
SIDs and STARs in radarcontrol.io
radarcontrol.io includes real SID/STAR procedures sourced from FAA CIFP data for US airports. You can:
- Issue
dv(descend via) to have an aircraft follow STAR constraints automatically - Issue
cv(climb via) for SID departures - Override individual constraints with
x GREKI 240(cross GREKI at FL240) - Cancel restrictions with
xp - Write JavaScript scripts that react to constraint events