The following is Alaska Airlines' policy on same-day flight changes:

Each traveller may apply for Alaska Airlines flight change policy on the same day if they match the requirements.

A verified flight reservation with Alaska Airlines is required.

Up to 48 hours before the departure of their last flight, passengers may seek changes.

It is not possible for passengers to change their home airport in order to connect to flights to other cities.

This law prohibits passengers from changing terminals to modify their tickets.

Passengers can change their flight via the standard flight change procedure if they are unable to meet the aforementioned requirements.

Also visit : American Airlines flight change policy