From DLNet:

Delta Cargo offers employee discounts for shipping pets
April 6, 2010

Delta Cargo is offering employees a discount for their pets traveling as cargo within the U.S.
A 20% discount now applies for dogs or cats that are shipped as cargo within the US. The discount is for shipping an employee’s personal pets only. Employees are eligible for the discount if they have at least one year of service with Delta, Comair, Compass or Mesaba.
The discount applies to pets traveling as cargo without the employee accompanying the pet. Pets traveling as checked luggage with the nonrevenue traveler will continue to be charged the full pet fee.
Fees are waived for pets traveling as carry-on luggage.
Shipments of pets and other animals depend on weather conditions where temperatures are not too hot or too cold.