May an airline change your departure date to a different day after you bought your ticket?
(Edit) This was with Frontier Airlines from Portland, OR to Denver, CO, USA. I called and they told me my original flight was canceled (even though it was still listed on their website as an option). They did agree to change it to a slightly more convenient time. But I will most likely not fly with them again.
The answer is YES.
But, there are some other factors you should be aware of.
Most airlines have a threshold on the schedule change which open some options
*Note, there may still be a fare difference on these options.
While uncommon, some reasons are:
Equipment shortage
Anticipated Weather
Anticipated Labor Action
A simple schedule change
Yes they can.
While terms and conditions vary, it's pretty much universal that an airline can make changes like that, or even cancel the flight. The only issue is what they have to do when it happens.
Virtually always for a change of departure by a day or more, the airline is obliged to give you a full refund. They may be reluctant to talk about this, (since they want your money) but if you ask them for a refund you should always be able to get one. Of course this may not help you if they make the change so late that alternative flights are not available, but it should be an option.
You have a few options if the new date doesn't work for you. One is claim the refund and find another flight. The other is to use the threat of a full refund to negotiate a partial refund. They might be prepared to refund you some of the money in order to keep your business.
Yes, they can, and occasionally they do. You may be able to demand a refund, but that won't help make your trip work. This is a very good reason to buy travel insurance. When (post Cyclone Pam) Air Vanuatu changed our trip by 2 or 3 days, I was able to get them to only change it by one day (no charge of course) and the travel insurance covered the extra night in the Vanuatu hotel. I was lucky that the next hotel I was going to just agreed to a later arrival date, even though that brought me under their minimum stay, but if, for example, they had insisted on being paid for the original night I booked and didn't use, the travel insurance would have covered that too.
If changing the date makes the trip just not work - for example you won't arrive in time for the event you are going to - then talk to your insurance company about whether you can book a different flight that does work, and claim for the cost. This wasn't an option for us because Air Vanuatu was the only airline flying between Vanuatu and Fiji and they were not running any flights on the day we had originally booked (they do 2-3 flights a week between those points.)
