some Falsehoods Programmers Believe via flightaware.engineering by Ben Burwell 02 Jun 2025

• Flights depart from a gate
• Flights that depart from a gate only leave their gate once
• Flights depart within a few hours of the time they were scheduled to
• Flights depart within a day of the time they were scheduled to
• Flights have schedules
• Flights take off and land at airports
• Airplanes (excluding helicopters) take off and land at airports
• Flights are at most a dozen or so hours long
• Okay, they're at most a few days long
• Flights are identified by a flight number consisting of an airline's code plus some numbers, like UAL1234
• Flights are identified by either an airline flight number like UAL1234, or the aircraft's registration like N12345, B6459, or FHUVL
• A flight identifier like B6459 is unambiguously either a registration (B--6459), an airline flight number (B6 459), or something else
• Flights don't have multiple flight numbers
• Flights with multiple flight numbers unambiguously have one “main” flight number
• A particular trip's flight number(s) never change
• The flight number shown on your ticket is what the pilots and air traffic control are using
• Flights don't use the code of some entirely unrelated airline in their flight identifier
• No flights use the same flight number within a day
• Surely at least no flights use the same flight number at the same time?
• Okay fine, separate flights from the same major passenger airline that depart within a few minutes of each other would not both have the same flight number… right?

• Airports never move
• Terminal and gate numbers have a consistent naming scheme
• Each runway is only used by one airport
• Airports always have two unique identifiers: a 4-letter Civil Aviation Organization (ICAO) code and a 3-letter International Air Transport Association (IATA) code
• Airports always have three unique identifiers: an ICAO, an IATA, and a regionally-administered location code
• The U.S. Department of Transportation assigns one canonical code to each airport it oversees
• No airports have multiple IATA codes
• The ICAO code for airports in the U.S. always starts with the letter K
• For U.S. airports whose ICAO code starts with K, the last three letters are its IATA code
• You can tell which geographic region an airport is in from its ICAO code
• Everything that has an IATA code is an airport
• Everything that has an ICAO code is on Earth
• Airports have at least one well-known identifier of some sort

• No two airlines share the same IATA code
• No airlines use multiple IATA or ICAO codes
• You can tell what airline is operating a flight by looking at the physical aircraft
• Airlines assign flight numbers to specific routes
• Airlines only assign flight numbers to flights they operate
• Airlines only assign flight numbers to flights

• Waypoint names are unique
• There is one agreed-upon definition of altitude
• Flight information from Air Navigation Service Providers is accurate
• Okay, /pretty/ accurate; they wouldn't indicate that a flight had departed unless it really had
• If they indicate that a flight plan has been cancelled, then that flight definitely isn't going to operate — it wouldn't simply be due to someone editing the flight plan
• At least their radar data accurately identifies each aircraft
• Radars with overlapping coverage areas agree on the location of a target they can both see
• If they send us a flight plan with the ICAO identifier of a known airport as the destination, then there must have been some intention of arriving there
• If an aircraft diverts to another destination, it won't divert again

• ADS-B messages only come from aircraft
• ADS-B messages only come from aircraft and airport service vehicles
• ADS-B messages only come from vehicles of some kind
• The GPS position in ADS-B messages is accurate
• The GPS position in ADS-B messages is accurate within some known uncertainty radius
• ADS-B messages always include the correct flight identification
• Transponders are correctly programmed to indicate the aircraft type (helicopter, airplane, balloon, etc)
• You can always determine a aircraft's registration number from its ADS-B messages
• Transponders are programmed with the correct Mode S address
• All of the transponders on a single aircraft are programmed with the same Mode S address
• Nobody will ever set their flight identification to weird things like NULL
• People will remember to update the transponder when the aircraft's registration changes
• ADS-B messages are always received exactly as they were transmitted
• No one ever transmits false ADS-B messages
• Transponders never break and rodents never chew through cables