Originally Posted by
London Dude
The prices you quoted above in GBP and USD are actually identical if you use Friday's London 4:00 PM fixing for the GBPUSD FX rate, which is what UK-based BA probably does.
https://www.bloomberg.com/markets/currencies/fx-fixings
After the UK/European markets closed on Friday there was a major sell-off in equities and the GBP also took a hit against the USD, so Friday's GBPUSD closing FX rate (the New York 5 PM fixing) was quite a bit lower than the London 4:00 PM fixing. If you used google or any FX websites when you made the GPBUSD conversion earlier, since the FX markets reopen at 10:30 PM UK time on Sunday, you would have applied Friday's closing price, which is the same as the New York 5 PM fixing, whereas BA applied Friday's London 4:00 PM fixing.
Needless to say this would have worked in the opposite way had the GBP risen against the USD after Friday's London 4:00 PM fixing.
Which is exactly what I said … that there is no differential anymore
The past differentials I was referring to, months/years ago related to different pricing levels, I never claimed it has anything to do with fx rates.
PS: Airlines don’t use their own convention for FX fixes. BA and nearly every airline on the planet use IATA consolidated exchange rates for fare conversions.