I thought that to be very fast for a pigeon. And indeed, https://en.wikipedia.org/wiki/Pigeon_racing#Breeding says:
“It is this selective breeding that has given rise to the racing pigeons of today, capable of finding their way home from over 1,600 kilometres (990 mi) away and flying at speeds in excess of 130 kilometres per hour (81 mph) with a tail wind, but average 60 kilometres per hour (37 mph) on a calm day”
The app also could use weather data to adjust the speed depending on prevalent winds. Once it has that, it also could increase the “do not arrive” probability for hard storms.