I was trying to mask some of the hairy details of our flight situation in my recent questions.
Two of us have flights JFK-TXL booked on AA ... which has a $150 change fee if you modify origin or destination, but nothing if you modify date. We're looking to have two more (ticketless) travelers join us. Unfortunately there's no award space on our currently booked flight, so we are considering:
(a) Find another open JFK-TXL flight (which may be tricky), or
(b) Book our friends on a JFK-ZRH flight. Change our AA booking to JFK-TXL with a the same connecting in ZRH ... and "miss" that last segment.
... so I'm just playing around with different options and coming across these differences in booking options.