FlightAware Discussions

Flight delayed or on time with Alert

Hi there

How would I figure out with a SetAlert for departure if a flight is indeed on time or not?

As I understand I get the departure time = takeoff time and an estimated landing time = runway touchdown. But how on earth would I be able to figure out with it if a flight is delayed or not?


There are various techniques for attempting to estimate it, but it is difficult to accurately estimate when any flight will precisely arrive since there can be many things en route that can further delay it (weather at the destination, number of other flights arriving at the same time, holding patterns, taxiway congestion, how much time ATC/pilots are able to make up in flight, etc).

However, a very simple method you can do: When you receive the departure alert, look at the estimatedarrivaltime and see how that compares with the originally filed arrival time (which you will need to compute from filed_departuretime+filed_ete). Generally more than 15 minutes difference is a good minimum threshold for considering something late, but that can vary depending on your needs.

If you want to see how the runway departure time compares to the original scheduled gate departure, you can use AirlineFlightSchedule to obtain the published schedule for a flight even weeks/months in advance, but be sure to account for taxi time difference between the gate and runway.

Thanks for the answer.

Meaning if I would like to derive from the departure alert an estimate of a early or late arrival I would need to do

  1. set the departure alert
  2. Get the alert
  3. do another query to get the filed_departuretime+filed_ete

We ourselves have the scheduled on/offblock times only.

PS: We do understand that it is difficult to calculate because there are many unknowns in the equation but in the end that’s the info a user wants, not the estimated runway touchdown time without expected taxi times taken into account.

That approach would work.

You could likely also be able to get the filed_departuretime+filed_ete at the time you set the alert, since that information is known in advance of the flight actually departing. If your application intends to call FlightInfoEx prior to setting the alert, then you might already have that information.