How long do crashed UFO's last?
Solution 1:
These are the timers for all game modes in hours taken from game data:
UFO_CRASH_TIMER = 48
TERROR_TIMER = 30
UFO_LANDED_TIMER = 30
ABDUCTION_TIMER = 30
Solution 2:
Based on some testing:
On Normal, I have observed several of scout-classed UFOs take between 24 and 48 hours before being "repaired" and disappearing.
On classic, I have observed two scout-classed UFOs taking between 24 an 30+ hours to disappear.
Small sample sizes, and I don't know if bigger ships are more or less likely to take off quickly.