Here are some important details:
Your pet must be at least 15 weeks old to travel on Delta.
Your pet must travel in a carrier with the dimensions: 18 inches (length) x 11 inches (width) x 11 inches (height) and, as with all carriers, your pet should be able to stand up, turn around, and lie down comfortably within the carrier.
For international flights, the maximum weight for a carry-on pet is also 20 lbs, including the carrier, making it the airline allowing the heaviest pets in cabin.
The cost to bring your pet onboard is $200 each way or $400 round trip.
For travel to the European Union, pets must have a microchip and a valid rabies vaccination certificate in order to fly with Delta. You will notice this is the same for the other airlines. This is because this is an E.U. rule and not exactly a rule specific to the airline itself.
Delta Air Lines offers accommodations for passengers traveling with multiple pets depending on the circumstances:
Two Pets in One Carrier: You may transport two pets of the same breed and similar size, aged between 10 weeks and 6 months, in a single carrier. These pets must be comfortable together and fit safely within the carrier. When these criteria are met, Delta considers them as one pet for booking and fee purposes.
Traveling with a Mother and Her Litter: A female dog or cat accompanied by her unweaned litter is permitted to travel in one carrier, provided the litter is between 10 weeks and 6 months old. There is no restriction on the number of animals in the litter under this policy.
When traveling with your pet on Delta Air Lines, the pet carrier is considered your carry-on item. Consequently, you're permitted to bring only one additional personal item, such as a purse or laptop bag, which must fit under the seat in front of you.
Delta Pet Policy
Delta is known as a moderately pet-friendly airline, though some customers have noted they’re less pet friendly than others on our list.
We had heard from others that Delta was an option for international flights. When I started to dig more into their size requirements, I noticed Milou may be too big, especially when some customers were complaining about the space being smaller than listed. If you have a smaller pet, though, this wouldn’t be a major issue.
***Important Thing to Note: pets are NOT allowed in the cabin on flights to or from the United Kingdom. The only exception is for trained service animals with the proper documentation. They are, however, allowed in the hold below the plane. Because we did not want to put Milou in the hold, we avoided all flights flying to the UK. This is different from Air France, who doesn’t allow pets to fly into the U.K. at all.