"Tag-on" Flights v Triangle Routes
 

Serving two destinations with one departure from a hub is relatively common way to serve lower demand destinations. Something I've always found curious, why do some airlines prefer to do this using "tag-on" flights (eg, BA in the Caribbean) where as other airlines prefer to run 'triangle' route patterns (KLM in South America, SN in Africa)?

My initial thoughts:

- Triangle routes are obviously better from a flight time / cycle perspective, although on short hops the difference is minimal.
- It's probably easier/cheaper to have all the crew in 1 city instead of having to nightstop in both downroute points of the 'triangle'.
- A triangle route only works where tee aircraft can turn-around pretty much straight away, where as hops can have a longer turnaround at the final destination if needed.

Any other ideas?

A triangle pattern will only make sense if the two destinations are reasonably close together and both can easily be served non stop (although prevailing winds will also need to be considered). Obviously the location with the longer runway can be used for the second stopover.

It might be necessary to have a longer stop at the end location in order to fit in with airport curfews, slot availability, etc.

It could also depend upon loads at the two stations and wish to fly non stop in both directions from the more important destination, particularly if nearer or if a rival carrier flies non stop.

The carrier may have fifth freedom rights between the two outstations which could be lucrative.

Back in the day, BEA used to fly a fair number of triangular routes, too.

I recall LHR-Sofia-Bucharest-LHR, LHR-Zagreb-Belgrade-LHR and even Birmingham-Glasgow-Edinburgh-Birmingham.

air2000 used to do LGW - St Thomas - Antigua - LGW
767-300

In the mid-00s, Alitalia used to operate Milan > Lagos > Accra > Milan, and I used it quite regularly because more oftan than not they OK'd my ID90.

The problem was that the the flight was nearly always 100% full leaving Milan, but more or less emptied and then completely refilled at Lagos - so the Accra stop would see maybe just four or five disembark to be replaced by just another four or five boarders.

A very expensive way to get 10 or so people to and from Accra.

And anyone who's done the West African routes will know what I mean when I say that with just 60 minutes on the ground in Lagos and 60 minutes on the ground in Accra, by the time we were back in Milan the cabin looked like a municipal garbage dump.

Going back a few years when in the morning an Air UK F27 would operate Stansted- Edinburgh-Glasgow-Stansted and the evening rotation would be STN-GLA-EDI-STN. Passengers on the GLA-EDI once in 19 minutes.