Below please see a memorandum of agreement regarding Loran that was signed in April 2003 by the USCG, FAA and DOT. 

Note it contains useful information and again indicates Loran is the best theoretical backup to GPS.  The signatories are very high level people within each group.  They are: Michael Jackson, who at the time was immediately below Secretary Mineta in the DOT; Vice Admiral Allen, third in command at the USCG; and Marion Blakey, Administrator of the FAA.