your guess is as good as mine

not sure how many missions are there per year or if the "emptying" happens in nov 00 or mar 01 - if you add mods with new missions its further away

This is what determines the number of random missions:

`determineAlienMissions();`

if (monthsPassed > 5)

determineAlienMissions();

For the first 5 months you get Alien Research + 4 random missions, for a total of 5 missions. In addition you also get Alien Terror once a month and, by the end of 1999 and beginning of 2000 (depends on the difficulty level) a Retaliation mission is added.

Starting on the 6th month you get 2 random missions per month, so 14 missions for 7 remaining months, for a yearly total of 19 missions in 1999. And on 2000, that's 24 random missions, with 5 missions remaining for 2001.

Of course, all of this applies only to vanilla since adding new random missions will push forward the March 2001 date.