American Airlines and JetBlue have terminated their interline traffic and frequent flyer programme accrual agreements.
The deal had included routes between Boston Logan International Airport and New York JFK.
Starting yesterday, neither US airline will now accept new interline sales for travel on the other carrier.
And, from April 1, passengers will no longer earn miles or points when travelling on eligible routes operated by the other airline.
A statement said: “All American AAdvantage miles or JetBlue TrueBlue points already accrued through this partnership will be credited to customers’ accounts and are not affected.
“The two airlines are working together to ensure these changes have little impact to customers.”
The move comes three months after an enlarged American Airlines came into being following the completion of its merger with US Airways (see news, December 9).
JetBlue will this year launch a new fully-flat business class seat, which will be fitted to new A321 aircraft serving transcontinental routes from New York JFK to Los Angeles and San Francisco (see news, October 7).