I believe it is a scripted random-generation "event" that is settup so that it changes and follows your aircraft constantly while you're in the area over a CV or over the strats. So, to answer your question, there is no travel time, it just spawns in a random pattern around your aircraft when triggered. I however do not know if speed, altitude over target, or evasive maneuvering has any impact on potential hits, you'll have to likely get that answer from those who wrote the script themselves if they feel the desire to indulge the information.