I finally write this post as a guide to pass this annoying bug in the Spaghetti Airport Mission because I believe that H&D 2 was a RARE MASTERPIECE like all other games from Illusion Softworks.

The problem is that random (often in difficult hard) the Schumann's documents is unobtainable

It doesn't matter what tactics/strategies you implement in this mission on the hard/very hard difficultly settings, the problem resides with the games' script called 'AF1_documents_assigner.scr'.

in either of these difficultly settings the script uses a random integer to place the documents in 1 of 3 possible locations.
the first location is in a cupboard next to girl picture on the wall in the hangar which is unobtainable.
the second location is on a table in one of the tents which is obtainable,
and the third location is in a cupboard next to a bed in the main building which is unobtainable.
so, as you can see, you have a 33% chance of obtaining the documents in either of these difficultly settings :(

Then to complete the mission you have to play the game only when the documents is on the table in the pilot's tent

However, I found a 10 years old discussion board and got some info to SOLVE the problem. The best thing to do is get in the jeep and head straight across the map then left down to the tents. Shoot the two enemies that come out and then check the table for the documents in the right hand tent. If they are there, grab them and save and do the rest of the level; if not restart the mission until they are. It takes about a minute to do this each time so not too much trouble if they are not there the first time.

I make a screenshoot of the only right location to complete the mission

ENJOY !!!!