"How late the departure was" calculation vs "departure_delay"



I need some help on how to interpret some values obtained via FlighInfoStatus (FlightXML3):

I have a flight that is currently enroute:

            "ident": "UAE406",
            "faFlightID": "UAE406-1520143500-schedule-0000",
            "airline": "UAE",
            "airline_iata": "EK",
            "flightnumber": "406",
            "tailnumber": "A6-EDC",
            "type": "Form_Airline",
            "codeshares": "QFA8406",
            "blocked": false,
            "diverted": false,
            "cancelled": false,
            "origin": {
                "code": "OMDB",
                "city": "Dubai",
                "alternate_ident": "DXB",
                "airport_name": "Dubai Int'l"
            "destination": {
                "code": "YMML",
                "city": "Melbourne, Victoria",
                "alternate_ident": "MEL",
                "airport_name": "Melbourne Tullamarine"
            "filed_ete": 48120,
            "route": "DCT ANVIX L223 TARDI N629 GIDAN/N0499F350 P570 KITAL L894 BIBGO DCT SUNAN L894 DADAR DCT KAMUN/N0491F370 DCT IDEVI DCT SAKEG DCT 10S087E/M084F370 13S090E/M085F390 18S095E 20S097E 25S103E 28S107E DCT ACOOL/N0484F390 DCT KEELS DCT 33S117E DCT MOLGA/N0483F410 DCT 35S124E DCT RIDLE DCT ROMPA DCT RUFLE DCT BUNGY DCT MTG Y53 WENDY V279 ML",
            "filed_altitude": 330,
            "display_filed_altitude": "33,000 feet",
            "filed_airspeed_kts": 501,
            "distance_filed": 7330,
            "filed_departure_time": {
                "epoch": 1520316300,
                "tz": "+04",
                "dow": "Tuesday",
                "time": "10:05",
                "date": "03/06/2018",
                "localtime": 1520330700
            "estimated_departure_time": {
                "epoch": 1520320200,
                "tz": "+04",
                "dow": "Tuesday",
                "time": "11:10",
                "date": "03/06/2018",
                "localtime": 1520334600
            "actual_departure_time": {
                "epoch": 1520321571,
                "tz": "+04",
                "dow": "Tuesday",
                "time": "11:32",
                "date": "03/06/2018",
                "localtime": 1520335971
            "departure_delay": 3960,
            "filed_arrival_time": {
                "epoch": 1520364420,
                "tz": "AEDT",
                "dow": "Wednesday",
                "time": "06:27",
                "date": "03/07/2018",
                "localtime": 1520404020
            "estimated_arrival_time": {
                "epoch": 1520367480,
                "tz": "AEDT",
                "dow": "Wednesday",
                "time": "07:18",
                "date": "03/07/2018",
                "localtime": 1520407080
            "actual_arrival_time": {
                "epoch": 0
            "arrival_delay": 4440,
            "status": "En Route / Delayed",
            "progress_percent": 31,
            "aircrafttype": "A388",
            "full_aircrafttype": "A388",
            "adhoc": false

From your FAQ I have these informations on how to calculate some data:

How late the departure was = (actualdeparturetime - filed_departuretime).
How late the arrival was = (actualarrivaltime - (filed_departuretime + filed_ete)).

If I calculate it then (using epochs):
How late the departure was = (1520321571 - 1520316300) = 5271
departure_delay is 3960

What you currently show in your site is the departure delay time, not the calculation time I’ve computed: https://flightaware.com/live/flight/UAE406

Same happens to “How late the arrival was” calculation and arrival_delay.

What value I should use?
Can you please revise and advise me on this?

Thanks in advance


departure_delay is not actual delay, that is why we mention to use the formula to calculate actual delay. departure_delay is a delay that is typically provided in advance which indicates filed_departure_time will not be made which is then reflected in estimated_departure_time.


I’m still not sure what value to use as departure delay .
You in your site, are showing departure_delay value at Origin, and arrival_delay at departure during flight time.
Still confused. Can you please explain me with an example?



Before actual_departure or actual_arrival happen, we can receive delay information. This is what would be departure_delay and arrival_delay. If you want actual departure delay or actual arrival delay, you should use actual_departure_time minus filed_departure_time and actual_arrival_time minus filed_arrival_time


Thanks, I guess I got it.

So, inthe case I’ve described, because the flight was en_route I should use the computed value (actual_departure_time minus filed_departure_time) and not the departure_delay that is not correct.
But, I should use arrival_delay because the flight has not yet landed. When the plan arrives, then I should use the calculation (actualarrivaltime - (filed_departuretime + filed_ete)) or your last formula ( actual_arrival_time minus filed_arrival_time), because arrival_delay could not be updated, representing the correct value. Is that right?


Correct. Unless you are computing using an actual value, think of the departure_delay and arrival_delay as estimated delays until you receive an actual departure time or actual arrival time to compute the actual delays.


Thanks. And just a suggestion. Why that value is not updated by your system when events occurs? After departure occurs, you update the departure_delay, and after arrival occurs, you update the arrival_delay…


Thank you for the suggestion, however, I believe we see those as 2 separate things. What delay was provided and what delay actually occurred.


Ok. So I guess in your site, you are not showing the correct departure delay time, because that specific flight was enroute and you were showing departure_delay value. Why don’t you show the computed (actual/corrected) value aswell? Thanks.


There is also gate departure time and runway departure time to consider here. It does not appear that the gate information is included in the result above.


I don’t know how to consider those times at client side for the calculation of departure delay times.
More, I only get actual_blockout_time (gate departure time) if i use include_ex_data in the request, available only in >= Silver plan. What about runway departure time?
Since I’m not yet using that plan, I can’t check those values to consider.
Anyway, I’ve said that the value you are actual present has departure delay for an enroute flight, is the departue_delay value, not the value calculated by (actualdeparturetime - filed_departuretime)

Example ( “faFlightID”: “AFR166-1520231141-airline-0046”):

(1 hour 12 minutes late) at departure, that corresponds to “departure_delay”: 4320,
But… applying your formula: “actual_departure_time_epoch”: 1520440980 minus “filed_departure_time_epoch”: 1520435700 gives 5280 corresponding to 88 minutes delay 1h 28 minutes


You seem to be looking at gate times from your screenshot. If you are using the API and dont have gate data, then your times are runway times.


Can you please explain this better? You are saying that (1 hour 12 minutes late) showed in the screenshot are the delay regarding gate departure time? and not actually the actual time of departure?


Correction, I mean filed departure time, not actual departure time.


NOTE: Sorry about the confusion I’m making using 2 different accounts pribeirojit and msousajit, but they refer same entity