One that always arises with our airline reviews in particular is how to upgrade after booking, but before check-in. While it's not always available, there are a few options you have depending on your ticket fare class, airline and booking platform.
1. Direct bookings with the airline
If you booked directly with the airline, it's very likely you'll see offers to upgrade your flight after booking. If it doesn't show up right away, check back a week or so later and keep checking. The prices will go up and down based on the availability and occupancy of the flight.
Let's take an example using American Airlines.
I recently purchased a one-way flight from Puerto Plata via Miami to Las Vegas. At the time, booking a business class fare was over $5,000 so I booked an economy ticket. About a week later, I accessed my reservation under my account and scrolled down to the bottom to see this offer:
Of course, $213 is quite low, but that's a one way upgrade fare for the Puerto Plata to Miami flight. If I click into the "buy now" offer, I'll see an additional upgrade offer for $531 from Miami to Las Vegas, aka the longer more valuable flight.
Regardless, this is still cheaper than having booked the business fare originally. In this case, I'll continue to monitor the upgrade prices as we get close to see if they do down. Upgrading via the website is a great option if you're looking to bump up to business class before your flight.
2. American Express Platinum Upgrade with Points
AmEx Platinum offers a service with select airlines and bookings that you can upgrade your international flight using AmEx points. While this won't cover every airline, they offer this service for flights on Air Tahiti, Etihad and more! If you have a bank of AmEx points burning a hole in your pocket, this is a great choice.
3. Texting or calling the airline
Not all airlines offer a texting service, but we have occasionally texted the airline directly and asked if the have any upgrade offers. Often, even if it doesn't appear online, they will have an offer via the phone or text. Locate their text-hotline on their website. For example, you can text Delta at any time using their iMessage service for iphone.