Further research... DL is using the IRS's terminology.
Alaska and Hawaii
As noted in the chart above, a reduced international facilities tax is imposed on departures only for flights between the continental United States, and Alaska or Hawaii. Cite: IRC § 4261(c)(3). See the discussion of Alaska and Hawaii for details on the calculation.
http://www.irs.gov/businesses/small/...rsonsAirAlaska
International Facilities Tax
Along with the section 4261(a) percentage tax and 4261(b) segment tax, the section 4261(c)(3) international facilities tax is imposed because the aircraft travels over international waters and/or the land of another country. (Note that section 4261(c)(2) provides an exception for transportation entirely taxable under section 4261(a). Because amounts paid for flights to and from Alaska and Hawaii are not entirely taxable under section 4261(a), that exception does not apply.) Thus, the international facilities tax is modified to reflect a specific Alaska and Hawaii rate. The tax applies to departures only.
http://www.irs.gov/businesses/small/...cilitiesAlaska