Moien Panalpina/SGC.
I think you got it in one. There simply aren't any spare 400s around,& Atlas have the production line sewn up for quite a while. I really can't understand what all the complaining is about.
If I may say so, we went from 4 -200s (3 x 271C ex TransAmerica, 1 x 228F ex AF (1974 vintage)) to the current 10 400s (2 more to come for the moment).
Are you in UK or LUX?
rgds Rat