For more information, please see the Import/Export Price Indexes frequently asked questions site at http://www.bls.gov/mxp/fact_sheets.htm.
Source: US. Bureau of Labor Statistics
Release: U.S. Import and Export Price Indexes
US. Bureau of Labor Statistics, Services Import Index: Import Air Passenger Fares - United Kingdom [IV14211], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/IV14211/, July 4, 2015.