Why would Buffett buys into airline business?

So the below video on CNBC, shows that Warren Buffett is really in the know on the purchase, so much so that he felt he was not doing justice to Southwest if he did not buy the airline's stock after buying the other big three i.e. Delta, American Airlines and United. This action also shows that he is picking industry and not really picking stocks as he bought all 4. (He puts more money actually into American Airlines)

http://video.cnbc.com/gallery/?video=3000567979

This obviously made a big turnaround that caused some of observers to be wondering why would Buffett buys into a low profit airline business?

Let me take some guesses:

- Things change, industry changes as well. From a fiercely competitive industry, it has now become somewhat more conducive for players to co-exist. Airlines have now become more aware of their costs as well. Flying is no longer a rich people's travel alone. It is towards the masses, hence the full-fledged are also cutting down on frills.
- Low cost of oil. One of the largest costs component is oil depending on at what price, oil comprise of around 30% to 50% of airlines operating costs. It seems that oil price at this low USD40 - 50 is here to stay for a longer period.
- Transportation is ever more important. In the age of Uber becoming mainstream as compared to old days "sapu-teksi" was illegal, there are many spaces or industries that are or could be affected. Hotels can be affected by AirBNB. Banks is in a precarious situation. (I do not know how to invest on banks, although I still feel it is not that bad, hopefully). Media has obviously been the one that has changed. Shop retail is affected by e-commerce.
The one that could be triumphing is transportation be it towards people transport or goods transport. People travel more and more - so much so that these people are constantly on the move. They do business from one city to another, one country to the other. Casual tourists are also growing above average economic growth.
This calls for roads, rail, air transport to be positively affected. But the way some of these companies do business have to change.
Cathay rebranded its DragonAir. Why?
SIA bought into Tiger Airways. Why?
(This does not mean these airlines can be purchased. See Cathay Pacific and SIA still, their returns have not been good.)
In US, it is about the same or could even be better. New airlines are now into a business that is mature but still growing healthily - in which point it refers to lesser competition from newcomers but healthier and not careless competition among the status quo airlines.
- lesser more obvious areas to invest in. As mentioned earlier, media, banks and additionally insurance may not be what they seem to be 20 years ago. It was different then from today.
- airline business can be structured differently more so today than the past. Airlines can be leasing planes and operate as an airline rather than owning planes and operating them. This will cause lesser stress towards balance sheet than the own and operate. In any case, I am seeing airlines having a mixture of both.