An AK might be a little large to escape notice; I just mentioned that because it's the stereotypical type of firearm for that part of the world.
On the other hand, it would be very easy to hide a pistol, compact/foldable rifle/shotgun, or 18" short sword inside an innocent-looking box. The only reason a box-cutter would be easier to hide would be its size; a box long enough to hold an AK would probably get noticed. But the other weapons I mentioned could probably have escaped notice if smuggled on by ground crews, and a few men with 18" short swords who were well-trained in their use would be able to hold at bay a plane load of even unwilling passengers.