Carrying Your Pet OnboardDue to space restraints, Frontier has very strict size regulations for carry-on animal containers. As a rule of thumb, the pet carriers must fit under the seat in front of you, while still allowing the animal to comfortably stand, sit, turn and lie down. Depending on the aircraft you will be boarding, the maximum allowable size of the carrier will differ.
For the largest plane, a Bombardier Q400, the container may be 17" long, 15.5" wide and 12.4" high. The smallest aircraft, an Airbus A318, A319 or A320 can only accommodate pet carriers that are 24" long, 15. 5" wide and 10" high. Embraers E190, E175 and E170 can house crates up to 18" long, 13.5" wide and 10" high, while pet containers must be 1" shorter and 1.5" narrower on plane models E135, E140 and E145.