IanAsiaTraveller

I've wondered for a while why the Avios I'm awarded always seems to be a little bit less than the minimum actual distance flown between two airports. Last week when we boarded at ATH, the screen display showed a distance of 1,509 miles to LHR. This corresponds pretty well with a "great circle" distance calculator on my computer which gives 1,511 miles. In fact BA award me 1,494 miles (exclusive of any bonus) for the journey. Although I don't have the figures to hand, I had a similar experience on the route to HEL recently too.

As the "great circle" distance is the minimum possible one between any two points, my question is whether BA have found some secret way of taking a slice through the earth's surface to calculate a shorter distance???

St Elmos Fire

Ground miles compared to miles flown at ~35,000 ft? The latter will be slightly further because of the curvature of the earth

Cymro

Do they do it from city centre to city centre?

I guess in some cases it could work in your favour, e.g., LCY-ORY is 5 miles further by the great circle than LON-PAR.

IanAsiaTraveller

Exactly. So how on earth can you get a distance LESS than ground miles??

Globaliser

This seems plausible, as ATH-LCY is 1,492 miles great circle.

Also, ATH-LON (using the LON metro area code) is 1,500 miles great circle, and ATH airport is about 12 miles to the far side of the city centre of Athens.

YacozA

For flights under a certain distance, we can assume BA ignores the GC and just measures a straight line through the earth connecting the two city centres.

St Elmos Fire

Good point! Circumference of the earth is 24,901 miles, the circumference of an orbit at 35,000 ft is about 20 miles more. I can see why the miles flown quoted onboard would be longer than the shortest ground distance.

The calculator you used may assume an average ground altitude above sea level, BA may assume sea level.

IanAsiaTraveller

Yes this does sound the most likely explanation, thank you. I will have to check on my next flight.

Worcester

Perhaps it's which ever "London" airport is closest. London Oxford heading west, London Southend heading east. Gatwick heading due south.

EsherFlyer

The Avios / TP calculator gives the same 1494 miles whether you fly LHR-ATH or LGW-ATH, so it looks like it's measured from Charring Cross or similar .

EsherFlyer

If you ask gcmap.com to plot LCY, LGW and LHR whilst drawing radii for 723mi@OSL,654mi@NCE in the Ranges box the place where those paths cross looks north of all the airports (and Charring Cross). It looks more "in the middle" if STN is added.

tigertanaka

There is no logic to it.

ARN-LCY (when BA flew the route) used to give 891 miles but ARN-LHR comes in at 890 miles despite probably 20 miles further to fly.

Great circle gives 894 for ARN-LCY and 911 for ARN-LHR so I guess Charing Cross would be around 900 miles so BA are short-changing me either way!

My guess would be that there is a table somewhere in BA's IT systems that has all the route distances hardcoded into it. When a new route is added, the award mileage has to be included but over the years this has been done by different people using slightly different calculation methods.

crazyanglaisy

There's also that oddity where BA thinks the distance to a destination is different to the distance back to LHR. I know that Boston flights have given me 1 less Avios for the return flight, and I think there may be a couple of other destinations thst are like this too.

Edit: tigertanaka got there before me!

tigertanaka

ARN-LON got you 891 miles each way for LCY and 890 for LHR no matter what direction you went.

BA's systems are seriously weird if you get a different amount for one way compared to the other.

LordBuckethead

Yes, almost... only the table and the logic are owned by Avios Group, not BA.