The Lumo delay indexes are a score from 1 to 10 given to each flight indicating how “risky” a flight is with respect to being delayed. The score is intended to capture both delay frequency (probability of a delay occurring) and delay severity (how long will the delay be if it does happen).
Quite simply, a delay index of 1 indicates near-certainty of less than a 30-minute delay, while an index of 10 indicates near-certain delay of 2 hours or more; the numbers in between are essentially a weighted average of the likelihood of a delay of different magnitudes.
Here’s a breakdown of how often flight delays have occurred historically given a delay index:
Let’s track one flight to see an example of how the delay index can be useful:
7 days from scheduled departure: Lumo indicates some risk of delay for your upcoming flight with a scheduled departure time of 9:26pm.
5 days from scheduled departure: Lumo sends an alert that the risk of delay has increased. Alternate lower-risk flight options are displayed.
19 hours from scheduled departure: Lumo let’s you know that it might be a good time to reschedule
15 hours from scheduled departure: Lumo let’s you know that a delay is certain, while the airline still hasn’t indicated anything.
3 hours from scheduled departure: The airline finally indicates that the flight will be slightly delayed.
This flight was actually delayed 5 hours and 1 min. Luckily, you’re smart enough to have rescheduled your flight or your plans thanks to Lumo, which indicated something was amiss well ahead of time, while everyone else is left waiting at the airport. You get a healthy night of sleep, and avoid a loss in productivity the following day.