Originally Posted by
ben237829624
This usually involves a reissue as the origin and destination have changed. You will be required to pay for the difference in fare if the new fare is higher than the original fare. However, the eligibility to do so and the change fee depend on the fair basis of your ticket.
This is not correct, presuming that OP is on a non-refundable/changeable ticket. When OP cancels, the entire value of his ticket will be a credit. He will then need to pay $150 in new money in order to access the credit. Depending on the value of the original ticket and the cost of the new ticket, this may or may not make a difference.
Before going through all of this, it is worth pricing out a new OW LAX-SEA. Sometimes its worth just letting the original RT go.
But, just skipping the first segment is not an option.