It gets more complex. Airbus have designed their A320, A330/A340/A350 planes with almost identical cockpits and handling characteristics to allow cross-crew qu

It gets more complex. Airbus have designed their A320, A330/A340/A350 planes with almost identical cockpits and handling characteristics to allow cross-crew qualification. A pilot with an A320 type rating can take a 7 day course to become qualified on the A330 (instead of the 40 day course normally required). And they can maintain the type rating on both types simultaneously. Since the A330 shares a type rating with the A340 and A350, this allows a pilot to fly quite a few airbus planes. Given the Max is so close to older 737s, I see no reason why Boeing and the FAA couldn't come to a similar arrangement, were pilots can be cross-trained with a 1 week course and maintain simultaneous type ratings on both the Max and Older 737s. Boeing does have a few common type ratings: The 757 and 767 share one; The 777 and 787 share another. But as far as I'm aware, pilots can only be qualified on one Boeing type rating at a time.