SriLankan Airlines has confirmed that it will officially join the oneworld airline alliance on 1st May. This will allow you to earn and spend Avios points (and earn British Airways tier points) when flying SriLankan.
SriLankan is not a large airline, operating just 21 aircraft to 20 countries from Colombo (below). It carried 4.7m passengers in 2013.
Routes include Heathrow, Frankfurt and Paris, Hong Kong, Bangkok and Tokyo, so it will open up opportunities for getting around Asia. There are also a number of flights to and from India and the Middle East.
Importantly, Colombo is also a key stopping off point for The Maldives, with Colombo being just an hour or so from Male. This opens up yet another potential redemption routing from London, and adds to the new Qatar Airways and Malaysia Airlines options that opened up when they joined oneworld. Colombo to Male would be just 4,500 Avios.
SriLankan also runs a number of flights out of Bangkok, heading to Shanghai, Beijing (these two are ending soon), Hong Kong and Gaungzhou. There is also a Tokyo to Male route.
British Airways resumed its own flights to Colombo last year after a number of years, tagging it onto the end of three existing flights to The Maldives each week.
I have never flown SriLankan myself, although feedback on their business class service out of Heathrow looks OK. They do have a number of new Airbus A350 aircraft on order, however, so I would expect to see major changes in the next few years. It will be interesting to see what sort of fuel surcharge, if any, are added to the London, Frankfurt and Paris departures.