What is a flight plan? ​

A flight plan is a document filed before departure that tells ATC where an aircraft is going, how it's getting there, and what equipment it has. Every IFR (Instrument Flight Rules) flight requires one. It's the foundation of everything a controller does with that aircraft.

What's in a flight plan ​

A typical IFR flight plan includes:

• Callsign - airline and flight number (UAL452) or tail number (N12345)
• Aircraft type - B738, A320, CRJ9, etc. This tells ATC about performance capabilities and wake turbulence category
• Departure airport - ICAO code (KJFK, EGLL, etc.)
• Destination airport - where the flight is going
• Route - a sequence of waypoints, airways, and procedures from departure to destination
• Cruise altitude - the requested flight level (FL350, FL380, etc.)
• True airspeed - planned speed at cruise
• Equipment/surveillance codes - what navigation and communication gear is onboard (GPS, RVSM, ADS-B)
• Estimated time en route - how long the flight will take
• Fuel endurance - how long the aircraft can stay airborne
• Alternate airport - backup destination if the primary is unavailable

How ATC uses it ​

The flight plan is loaded into the ATC automation system before the aircraft even pushes back. When the controller sees a data block on the radar, the flight plan data is right there - callsign, aircraft type, assigned altitude, destination, route of flight.

Controllers use the route information to anticipate where traffic will go. If UAL452 is filed via J80 MERIT direct JFK, the controller knows that aircraft will be heading toward MERIT and can plan separation with other traffic on that route.

The cruise altitude helps controllers assign flight levels. If an aircraft filed for FL370 but the controller needs FL350 for spacing, they know FL370 is the pilot's preference and can try to accommodate it later.

Equipment codes matter too. If an aircraft isn't RVSM-equipped, it can't fly between FL290 and FL410 with standard 1,000ft separation. If it lacks GPS, certain direct routings aren't available.

Filing and amending ​

Pilots (or their dispatchers) file flight plans through automated systems. In the US, flight plans go into the FAA's TFMS (Traffic Flow Management System). In Europe, they go through Eurocontrol's IFPS (Integrated Initial Flight Plan Processing System).

Routes can be amended in flight. A controller might say "cleared direct MERIT, rest of route unchanged" - this modifies the active route while keeping the rest of the filed plan intact. Departure and arrival routes often follow published SIDs and STARs. Pilots can also request route changes, and controllers approve or deny based on traffic.

In radarcontrol.io ​

Aircraft spawn with pre-assigned routes and cruise altitudes. The flight plan data is visible in aircraft.plan, which includes the route, exit point, and requested altitude.

Flight plans are generated by the sim's traffic engine - you can't file them yourself. But you can modify the route: direct MERIT skips all waypoints before MERIT, setRoute replaces the entire route, and you can reroute aircraft around weather or congestion just like a real controller would. The exit point and exit altitude remain fixed.

Related: What is a SID and STAR? | What are airways? | What is a flight level?

Guides: Command reference | Quick start guide

Play Chicago Center - manage flight plans and route aircraft through busy Midwest airspace.