I've tried running it with both exec and execVM. I've also now tried running it in both .sqs and .sqf format.
In .sqs using the exec command in the trigger "on act" line it works fine with no errors if I don't add the delay commands to the script (but of course all the AI disembark simultaneously).
I've tried starting lines2,3 and 4 with the ~delay time (eg ~2; at the start of line 2Â etc) and tried putting the delay between each statement, as seems to be suggested in the Wiki like this:
a2 action["GETOUT",bus1]; unassignvehicle a2;
~2;
a3 action["GETOUT",bus1]; unassignvehicle a3;
~4;
a4 action["GETOUT",bus1]; unassignvehicle a4;
~6;
a5 action["GETOUT",bus1]; unassignvehicle a5;
In sqs format any addition of the ~ statement returns an error (black box in top left of the screen when the script is called ingame) that just quotes a part of the script and says "Generic error." The script will still run but the AI will all exit the helicopter simultaneously.
In sqf format, if I can get it to run at all, the code error box is far larger and usually only the first AI infantryman (the one who's line has no delay) will disembark. Unfortunately the error box disappears before I can note down the error message. (as per the content of the Wiki, in sqf format I change the "~" to "sleep").
I should have mentioned in my original post that I'm totally new to the editor, only having had ArmA since the UK release. I suspect I'm doing something really stupid here.