Item 2. PROPERTIES

Flight Equipment

Our operating aircraft fleet, commitments and options at December 31, 2018 are summarized in the following table:

The following table summarizes the aircraft fleet operated by regional carriers on our behalf at December 31, 2018:

Aircraft Purchase Commitments

As part of a multi-year effort, we have been investing in new aircraft to provide more premium products, an improved customer experience and better operating economics. Our purchase commitments for additional aircraft at December 31, 2018 are detailed in the following table:

Ground Facilities

Airline Operations

We lease most of the land and buildings that we occupy. Our largest aircraft maintenance base, various equipment maintenance, cargo, flight kitchen and training facilities and most of our principal offices are located at or near the Atlanta airport on land leased from the City of Atlanta. We lease ticket counters, passenger holdrooms, operating areas and other terminal space in most of the airports that we serve. At most airports, we have entered into use agreements which provide for the non-exclusive use of runways, taxiways and other improvements and facilities; landing fees under these agreements normally are based on the number of landings and weight of aircraft. These leases and use agreements generally run for periods of less than one year to 30 years or more, and often contain provisions for periodic adjustments of lease rates, landing fees and other charges applicable under that type of agreement. We also lease aircraft maintenance, equipment maintenance and air cargo facilities at several airports. Our facility leases generally require us to pay the cost of providing, operating and maintaining such facilities, including, in some cases, amounts necessary to pay debt service on special facility bonds issued to finance their construction. We also lease computer facilities, marketing offices, reservations offices and other off-airport facilities in certain locations for varying terms.

We own our Atlanta reservations center, other real property in Atlanta, and reservations centers in Minot, North Dakota and Chisholm, Minnesota.

Refinery Operations

Our wholly owned subsidiaries, Monroe and MIPC, own and operate the Trainer refinery and related assets in Pennsylvania. The facility includes pipelines and terminal assets that allow the refinery to supply jet fuel to our airline operations throughout the Northeastern U.S., including our New York hubs at LaGuardia and JFK.