FlightAware Discussions

API vs Website QTR8970 - "late" calculation

As for today, querying API FlightXml3 » FlightInfoStatus QTR8970 we got the following flight occurring:

                "ident": "QTR8970",
                "faFlightID": "QTR8970-1615200600-schedule-0159",
                "airline": "QTR",
                "airline_iata": "QR",
                "flightnumber": "8970",
                "tailnumber": "A7-BFL",
                "type": "Form_Airline",
                "blocked": false,
                "diverted": false,
                "cancelled": false,
                "origin": {
                    "code": "OTHH",
                    "city": "Doha",
                    "alternate_ident": "DOH",
                    "airport_name": "Hamad Int'l"
                "destination": {
                    "code": "VVTS",
                    "city": "Ho Chi Minh City",
                    "alternate_ident": "SGN",
                    "airport_name": "Tan Son Nhat Int'l"
                "filed_ete": 25800,
                "filed_airspeed_kts": 453,
                "distance_filed": 3729,
                "filed_departure_time": {
                    "epoch": 1615372800,
                    "tz": "+03",
                    "dow": "Wednesday",
                    "time": "13:40",
                    "date": "03/10/2021",
                    "localtime": 1615383600
                "estimated_departure_time": {
                    "epoch": 1615379754,
                    "tz": "+03",
                    "dow": "Wednesday",
                    "time": "15:35",
                    "date": "03/10/2021",
                    "localtime": 1615390554
                "actual_departure_time": {
                    "epoch": 1615379754,
                    "tz": "+03",
                    "dow": "Wednesday",
                    "time": "15:35",
                    "date": "03/10/2021",
                    "localtime": 1615390554
                "departure_delay": 2340,
                "filed_arrival_time": {
                    "epoch": 1615398600,
                    "tz": "+07",
                    "dow": "Thursday",
                    "time": "00:50",
                    "date": "03/11/2021",
                    "localtime": 1615423800
                "estimated_arrival_time": {
                    "epoch": 1615403340,
                    "tz": "+07",
                    "dow": "Thursday",
                    "time": "02:09",
                    "date": "03/11/2021",
                    "localtime": 1615428540
                "actual_arrival_time": {
                    "epoch": 0
                "arrival_delay": 2340,
                "status": "En Route / Delayed",
                "progress_percent": 19,
                "aircrafttype": "B772",
                "full_aircrafttype": "B772",
                "inbound_faFlightID": "QTR8951-1615170840-schedule-0259",
                "adhoc": false

As you can see, filled departure time, which is marked as “time”: “13:40”, (the initial planned time), is mentioned your website 2 lines below Takeoff as Scheduled time. The flight actually departed at “time”: “15:35”.

My question is how do you determine that the flight is 39 minutes late? With the API response I can achieve the “39 minutes late” that is appearing on the website by consulting “departure_delay”: 2340 (seconds) which is 39 minutes.

But if I calculate the difference between actual time of departure and filled departure time, it gives me 01h 55m late departure. Is this incorrect calculation/thinking?

So, why the flight is late 39 minutes and not 1h55 minutes late?


The calculation is the difference between filed_blockout_time and actual_blockout_time which are found in the EX data which is an addition to the FlightInfoStatus call which requires a Silver plan.

This scenario is likely to occur if we get an update for the gate departure time, but not the runway departure time.

Hello @cbw,

Thanks for the response. So, in your opinion the flight is not 1h55min late because FA recieved an update for the gate departure but not for the runaway departure time. I thought that those updates were ment as “estimated” dates (ETD), not Scheduled (STD). I thought that receving some updates hours before the flight planned to occurr, meant to be treated as estimated (flight is not ocurring at 13:40 as planed, but will go to departe (estimated) at 15:35 (It actually departed at 15:35, like the time present on ETD).
I still dont get it why you consider tthat de difference between actual departure time and the new date time estimated for gate departure, as the delay time.

Trying to get you some additional insight into this. I will be back with some more information after speaking with our engineers.

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I’ll wait for more details.
Thanks @cbw.

Sorry for the delay. We use that as our standard as most commercial carriers use block in and block out as their times for departure and arrival and not runway times.

Thanks @cbw. From our side implementation we still have doubts on what we should use for showing delay times: if it makes sense using departure_delay that internally is based on the difference between filed_blockout_time and actual_blockout_time or if we use other calculation based on STD and ETD/ATD, so what’s the point of having STD?