You will have more flexibility, if you buy your ticket from British Airways. You can cancel your ticket and receive a refund under British Airways cancellation and refund policy. If you cancel your ticket within 24-hours of booking, British Airways will not charge you any cancellation fees.
****s://flightcancellationpolicy.com/british-airways-cancellation-refund-policy

If you purchase tickets in the first and main cabin class and you have to cancel your flight for whatever reason, you won't be charged a flight cancellation fee according to Alaska Airlines' cancellation policy. However, there is no need to pay additional costs, if you meet the 24-hour cancellation requirements. You receive travel credit points from the airline, which you can apply to your subsequent reservations.
****s://flightcancellationpolicy.com/alaska-airlines-cancellation

When changing a flight, the customer must follow certain flight change policies and getting information about these policies is essential because it will let you know whether you have to pay a change fee or not. If you don't know about Avianca flight change policy, please review below.

Avianca Airlines will only accept a flight change request if there are seats available on the newly selected flight. If the airline is delayed by more than 3 hours for its own reasons, you have the opportunity to change the flight for free.
****s://flightcancellationpolicy.com/avianca-change-flight

You may bring one bag and one personal item for free in accordance with JetBlue baggage policy. In Basic or Economy class, there is no need to pay additional charges, if you carry two small bags. In Basic or Economy class, you can bring two small bags without incurring luggage costs. The carry-on luggage weight & size are subject to specific requirements. If your weight is less than 50 pounds, you may avoid the excess baggage fee. You will be responsible for the excess baggage fee, if carry more than two bags. If you bring any restricted or harmful items in your luggage, the airline may deny your boarding request.
****s://flightcancellationpolicy.com/a-guide-to-jetblue-baggage-policy