Interest based bargaining (IBB) is a framework to reign in labor demands. If the RLA constraints were removed and there was real power on both side there would be more timely deals and openers would be more reasonable because you are actually bargaining for a specific time frame and not an open end undefined contract duration. IBB focusses on solving managements "problems." It's been the buzz word of choice for going on 3 decades now. All the training focuses on problem solving and mutual benefit which is great but the meat of a contract, pay and work rules, will always be in opposition which is why they are last and take the longest.