I disagree. For flying/extended travel, when they are not being watched, I don't think that the ferret cage would be a good idea.
Plastic is OK for short term travel, when you are monitoring them in case they start chewing, but on a long-term basis, they could chew their way out.
I learned that the first time that I put Mr. Whiskers in the cat carrier while I cleaned his cage. He managed to chew a substantial hole in the carrier near the door.
I say, metal only...better safe than sorry!!! :thumbsup:
ETA: MY BAD!!! I got this thread confused with the one where the person is moving and flying his chins.
(Mods/Admin -- if possible, please delete. THANKS!!!)