The logic matters little, probably less than your opinion. The authorities of the world have agreed that the age 60 limitation for airline pilots is no longer valid, if it ever was. Some authorities think there should be no limit, some think it should be 66 or 67, some think it should be 65 with no other restrictions, some think age 65 with the one pilot under the age of 60. It has been agreed to use the age 65 with the one pilot under age 60 rule until more data can be collected. 
All Defined Benefit retirement plans, including Social Security, are under threat at all times. The problem is that unions in the post WWII days until recently, when America was the only real industrial power, have negotiated very generous retirement packages for employees who now days live ten years longer than they used to. Example: At General Motors workers can retire at age 48 with 30 years of service and collect 80% of pay for very possibly 30 years to a typical life expectancy of 78. In other words a typical worker can work for 30 years and retire for 30 years. How can this continue? It can not, if GM is to survive and stay competitive with the global market for car production. So the same is true for the Airlines and their DB programs. The American airlines must compete in a world market and a domestic market too. If United, SW, Jet Blue, Air Tran, Delta, US Air, NWA, Frontier, all the Regionals and soon Virgin America all have DC plans, how can any American airline maintain a DB plan with pilots being hired at 40 years old and then retiring at 60, then collecting a generous retirement for possibly 20 or 25 more years.
