# How to differentiate two flights with the same flight number that arrive on the same day?

I'm currently working on a piece of software that includes flight information. I have access to flight schedules and I'm making each days flight unique based on flight number and the date that it arrives.

I've hit a problem trying to differentiate flights that arrive on the same day though.

Example:

On Sunday, Flight LS1494 leaves at 19:50 and arrives the next day at 00:25.

The next day, on Monday, LS1494 leaves at 16:40 and arrives at 21:15, making it arrive twice in one day.

Is there a standard way to differentiate these? I have one source of data that includes an "Operational Suffix" of "B" for the flight that originally left on Sunday but I'm not sure if that is actually relevant.

I could include the actually arrival time to identify them however sometimes that scheduled time changes and doesn't get updated immediately which can cause problems.

• Possible duplicate of: aviation.stackexchange.com/questions/14382/… – Brilsmurfffje Mar 10 '20 at 9:29
• That question seems more specific to ATC callsigns. My problem is more related to the flight schedule and flight number and how they are handled in advance of the flight actually running (potentially months in advance). If ATC only decide on the day to change the number then I don't think I can handle that in advance – Scott Bamforth Mar 10 '20 at 9:36
• That differs from airline to airline, I know that KL592 JNB-AMS leaves just before midnight. If that flight is delayed than it receives a new flight number. The main reason being that if something happens to the flight, the relatives on the ground know for certain if there loved one is on the flight or not. – Brilsmurfffje Mar 10 '20 at 9:38
• It's probably covered in an IATA standard, those typically run for \\$2,000 or so. Hopefully you'll get an answer. I agree it's not a duplicate. – ymb1 Mar 10 '20 at 9:48
• From a software engineers point of view, add the date and time to your key to make it unique... – MartijnICU Mar 11 '20 at 14:50

I'm making each days flight unique based on flight number and the date that it arrives.<

A standard used by some (most?) airlines is to refer to the flight by the Flight No and by the departure date (you've already discovered the problem with using arrival dates).

So your example flights would be LS1494/<Sunday date> and LS1494/<Monday date>.

• To further this, I would think that you would use the scheduled departure date, not the actual departure date, as late evening flight can obviously be delayed past midnight. – FreeMan Mar 10 '20 at 11:55

When working with flightplan interfaces between different ATC systems, we have usually set the unique identifier for a flight plan to be CALLSIGN + ADEP + ADES + EOBT + EOBD. (Meaning callsign, departure airport ICAO code, destination airport ICAO code, estimated off-block time, estimated off-block date.) For your example with the same callsign, departure and arrival airport, your differentiating attribute would be the time plus date for departure.

BTW, there are some Eurocontrol standards that are freely avaiable, such as OLDI: https://www.eurocontrol.int/publication/eurocontrol-specification-line-data-interchange-oldi, but I couldn't find a definitive answer there immediately.

• Using those five elements also deals with "direct" flights, i.e. multiple legs that share a flight number. – StephenS Mar 10 '20 at 22:35