The issues are number of guns versus weight. Americase has gotten the nod over the flat cases by ICC, Kalispel, etc. due to less flex and better side protection for carrying two guns. A couple of other companies provide similar cases such as Strong.
Once more than two guns must be carried, the vote generally goes to the TuffPak compact case. (Most of the manufacturers use TuffPak from I've seen.) It is tough enough and holds enough without weighing off the charts for airline travel. Generally, something like a Boyt or Hulme takedown padded slip is used on the guns inside. Clothing can make up the rest of the packaging although this is a pain if TSA wants to look at the guns.
There is a school of thought that one should minimize the risk of theft or damage by shipping guns separately.
