If it's a legally binding contract then it becomes a lawsuit. Delta sues when someone breaks a contract. If the contract is well written, a judge will decide in favor of those who were harmed. The key is unambiguous language that has a tangible penalty attached to it and union leadership that is willing to enforce the contract.

Delta sues Pratt & Whitney over parts deal | www.myajc.com

Delta Sues LAX, City Over Airport Terminal Lease - Law360

Delta Air Lines threatens legal action against city if it doesn?t find room for carrier at Dallas Love Field | Dallas Morning News

U.S. airlines sue travel clubs for appropriating airline logos - The Washington Post

| Delta sues Greenbrier over flights to Lewisburg

Delta sues US Export-Import Bank over loan guarantees | Finance & Data content from ATWOnline

American, Delta airlines sue travel clubs, allege deceptive practices

and of course Delta gets sued by businesses, government, people each year as well. It's part of doing business.