Each airline has different regulations when it comes to pet passengers. Some airlines allow small dogs inside the cabin, but they have to be kept in specially designed crates in the cargo hold in the case of large pets. For pets inside the cabin, most airlines would require the carrier to fit beneath the seat, have a waterproof bottom, ventilation, and enough space. So, you have to choose the best dog travel carrier having all these features. On the other hand, the ones travelling in cargo must have a metal door, hard sides, and the owner’s name attached.