Can someone explain mileage upgrades to me please?

Looking to book Upper Class returns to/from LAX - there are Gs available for our dates but don't have quite enough miles so I figured I'd look into booking economy or premium flights and then upgrading them.

How do I do this?

Do I book the economy/premium tickets on the exact flights the 'G' tickets are showing available for and then immediately call flying club to apply the mileage upgrade and pay the extra taxes? Is there a way I can work out the extra taxes? If the Gs go between the time I book the economy/premium tickets and the time I call flying club to do the upgrade, can I cancel (e.g. is there a 24 hour cooling off or anything?)

Sorry for all the questions but have never used miles to upgrade before. Thanks!

If you see G availability, it's best to do it all in one go on the phone. Give FC a call and have them price up everything for you (i.e. lowest upgradeable Economy and/or PE ticket + fees + taxes + mileage required), and ask them to confirm what you will receive in Miles and Tier Points. I find it best to write down everything as they go through the options.

The other thing to price in order to get the full picture (and you can do this yourself online) is the cost of simply buying miles to make up the difference you need.

Once you have all the data, you can make a decision based on cost, miles required, and miles and TPs received (if any) after the flights are taken.

I've always found FC to be helpful and patient on the phone. You could possibly ask them to hold the Gs you need (via one of the EC or PE upgrade options) for 24hrs whilst you consider all the options.

I would just call right now and do it all over the phone You can pay for the tickets and upgrade with miles in one transaction. They can hold the Gs for you so they won't go while they do the transaction.

Edit: NYLON beat me to it

Edit: NYLON beat me to it

Quick off the draw!

I would do it all in one call.
Not all fares can be upgraded. It costs nearly as much for an upgradeable economy as the cheapest PE.
How far short are you for miles?
It may work out cheaper to buy the extra miles you need and just do a full reward booking.
Have you done any flights in the last 6 months that will let you buy via miles booster? you can buy up to 2 x the miles you earned for £10 per thousand instead of £15
I would make the phone call and get the booking agent to work out the best option for you. I have always found them helpful.
Dick D

its easier to upgrade from Economy now due to all Economy classic and delight fares being upgradeable, so the initial Economy fare is much cheaper compared when you had to buy a very expensive one before the change.

its easier to upgrade from Economy now due to all Economy classic and delight fares being upgradeable, so the initial Economy fare is much cheaper compared when you had to buy a very expensive one before the change.

Thanks for that. I was unaware of the change.
I will have to do some sums in future to work out the most cost effect use of miles since I'm about to drop from earning two miles per £ down to .75

Dick D