On Monday I was at Ezeiza to "ship out" my guests and standing in queue there was a lady with a cat in a carrier boarding the plane. The cat was in a backpack with wheels and a retractable handle, such as those backpacks for kids that are to be carried by hand rather than worn over.
It was specifically for pets since it had openings with a solid net. I have to say that the adult cat (about 4 kg) looked a little constrained in there. I can't tell if the cat was flying on Alitalia to Rome as my guests, since it was on a different queue than my guests and AFAIK Alitalia doesn't accept pets aboard (at least until last year it didn't).
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http://articulo.merc...-perrogato-_JM]
Each airline has their rules about carriers: some want it soft, often want it hard, etc.
I have a Sturdi Bag bought in Europe (and made in the US) but there is a cheaper option called Sherpa (
http://www.amazon.co...1_t1_B002N65VPI)
What airline are you interested into?