Contracts
Where a frequent flier contract allows unilateral modification of benefits, and those fliers qualifying for a frequent traveler benefit are told that the rewards will change from year to year, the airline does not breach the contract by precipitately reducing benefits.
Concurrence: There are some grounds for acceptance of unilateral offer to modify the base agreement by flying a set number of miles.
http://media.ca7.uscourts.gov/cgi-bin/rssExec.pl?Submit=Display&Path=Y2016/D01-06/C:15-1845:J:Manion:aut:T:fnOp:N:1683060:S:0
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.