Frontier Airlines is an American ultra low-cost carrier headquartered in Denver, Colorado. The eighth-largest commercial airline in the US, Frontier Airlines operates flights to over 100 destinations throughout the United States and six international destinations, and employs more than 3,000 air-travel professionals. The carrier is a subsidiary and operating brand of Indigo Partners, LLC, and maintains a hub at Denver International Airport with numerous focus cities across the US. In August 2018, Frontier began connecting passengers with Mexican low-cost carrier Volaris under a codeshare agreement.
After making a codeshare agreement with Lufthansa that went into effect in 2010, jetBlue transitioned to the Sabre reservation system used by Lufthansa, enabling the airlines to sell tickets on each other's flights, transfer luggage and passengers between the two carriers, and combine frequent flyer programs,. By making use of JetBlue's North America routes as a feeder network, the agreement put Lufthansa in a position to operate quasi-hubs in New York–JFK and Boston Logan.