answer:Some airlines will give you a lower fare if the whole trip is on that airline. A better way to save on a trip like this is to check fares a day or two before and after your planned trip. If you can be flexible, it will help you get the most affordable fare. I booked a trip last labor day, San Francisco to NY on Monday (the holiday), drive to Boston on Thursday, Boston to SFO on Saturday. A week before we left, my son decided to fly Boston to Washington DC on the Saturday, then fly Dulles to SFO the next Tuesday. Even after change fees, we got a small refund because the flight to DC plus the day change for Dulles to SFO was much less than the original Boston to SFO flight.