Hi everyone,

I'm a frequest reader of FlyerTalk but a first time poster. I've spent a lot of time lurking on these forums, reading stories, dreaming of more luxurious travels, window shopping the advertised deals, reading reviews and stories... though I sometimes get lost in many complicated discussions and acronyms.

I've had the luck of a couple upgrades to business, but I've never purchased business tickets before, and I might just be able to take the plunge.

I'm looking to treat my partner and I to a long trip from the UK to Brisbane (home) once this pandemic is over...

I'm hoping some of you experts might be able to help me understand the intricacies of changing flight dates after booking. It's quite a long post, so

TLDR:
How do you calculate the fare difference between return flights? Is there any way to know what the difference will be in advance?

Full story:

I've noticed the best deals from Europe seem to leave from OSL, which we can get to easily. Though we'd like some flexibility on the date we will return, since it's quite a long holiday we're planning.

Plugging in some random dates for the future for an example, the per person fares I seem to see are:

OSL -> BNE (return) via CPH and SIN (Dep 1 Dec, Return 1 Mar)
Lite
NOK 25,319 £2,081.27 Change NOK 2,486 £204.35 Cancel N/A
Standr.
NOK 31,089 £2,555.58 Change NOK 1,491 £122.56 Cancel NOK 2,486 £204.35
Flexi
NOK 36,946 £3,037.04 Change *?Free?* Cancel NOK 1,988 £

At first glance, it looks cheaper to buy the Lite fare, and just pay the £204.35 change fee?

After selecting the Lite flight, then clicking Fare Rules, it states:
"Itinerary Change Allowed
With payment of NOK 2,486 and any fare difference, subject to currency conversion and your bank's exchange rate. Fees shown here are indicative. As the original fees are based in US dollars, the actual fees may vary due to exchange rate fluctuations. The original fees can be found on the ticket of a confirmed booking."

And checking on the Flexi rules:
"Itinerary Change Allowed
With payment of any fare difference, subject to currency conversion and your bank's exchange rate."

So it looks like both types of ticket also have fare difference calculations?

My first question is, how does the fare difference get calculated?

For example, if we booked the original return flight in the Standard fare type on the 1st of March, then on the 15th of Februrary, we decided we wanted to stay until the 1st of April instead, how would we calculate that?

If I look at one way flights from BNE -> OSL on that date, the fares are ridiculous! For example, the Standard fare is AUD 5,556.98 and the Flexi is 6,421.98! (Also, there are no "Lite" fares either!) So that can't be the right way to calculate it... If I use the original booking (OSL -> BNE 1 Dec), then change the return flight to 1 April, then the fare difference is minimal (NOK 72,978 vs 73,020). Is that how the fare difference is calculated?

Would they use the historical price when calculating the fare differences? (e.g, what the price would have been on the date the fare was originally booked... That would give us some kind of certainty about what sort of price the change of flights would actually be)- Or would they use a new price? Can anybody give me some examples of how I could calculate these differences?

I'm obviously concerned that the return price may increase dramatically, so much so that the "complimentary" booking change they offer on the Flexi fare wouldn't be worth jack.

When we finally have a date we can travel, are we better off buying the Lite fare on the OSL -> BNE leg, then a standard or a flexi for the return?

Finally, can anyone help me understand how cancellation fees calculated? (I did notice that the rules say that the more restrictive fare type applies to cancellations, so it means we can't use a Lite fare for the journey)... If we were to book the entire trip on Business Standard at a total of NOK 31,089 for 2 people, then we cancelled the return flights (at their advertised cost of NOK 2,486 per person), would we get NOK 13,058 back? (31,089 / 2 - 2486)? That seems to fair?

I notice that after selecting Standard fare for the outbound flight, then when selecting the booking type for the return flight, it shows "+ NOK 2,885". Is *that* the "price" of the return flight? Would we only get NOK 399 back if we cancelled? (2885 - 2486)?

I seem to just be confusing myself so far.

I appreciate this is a long post, so if you've got this far, many thanks for staying with me!

Keep well everyone, stay safe, and hopefuly we can all travel again soon!

Regards,
Gundof.