People confuse labor law and contract law all the time. In fact ALPA has done a great deal to non/mis-educate the pilot group on what their legal rights actually are, especially during bankruptcy.(see TWA pilots vs ALPA) Delta may have had unlimited whatever in 1990 prior to later contracts, but labor law would have prevented Delta from operating those planes without Delta seniority list pilots. With contract law, it would have been okay, but with labor law, not okay. To get around labor law, section 1 has to have a very specific set of instructions on what management is permitted to do. In fact, the most iron clad section 1 scope agreement that can ever be achieved by a pilot group is actually a blank section 1.