Originally Posted by IrishNJ

Not sure what you're saying here (meaning I'm open to learning something new) . I don't know anything about American but if I remember correctly; Continental had 757's with 255,000 LBs MTOW while United’s are only 240,000 so basically they can't use United's 757's to bail out any Europe mx cancellations.

Similarly, in the case of JB, you keep your spare XLR/LR doing BOS-MCO turns and if there's an issue you use it for Europe and replace that tail on the BOS-MCO route with your spare all-core 321. I don't see the difference.