Here is my list, in order of importance:
(1) Sept. 11. The impact of this day was more than just on the airlines, although it is hard to think of any industry affected more.
(2) The Lockerbie tragedy. Until 9/11/01, no event showed the vulnerability of airline security like this disaster in 1989. Also hastened the demise of Pan Am, a truly historic and identifiable airline.
(3) As stated before in this thread, the decline of flag carriers and major airlines. Some major carriers struggled and were gone by the early '90s, such as Eastern and Pan Am. Then after a brief boom period, most major carriers were ailing again well before 2001. We have since seen several major carriers in Chapter 11 (AA, UA
, US) or cease operations (Swissair, Sabena), while some historical names disappeared through acquistion (TWA, Canadian, British Caledonian).
(4) The rise to prominence of a new breed of low-cost carrier. Perhaps this point has a lot to do with (3), or maybe is a result of it. It seems every country in the world has at least one LCC fighting its flag carrier(s). In the USA, Southwest expanded to become a true coast-to-coast carrier, as well as newer low-cost carriers being born (AirTran, JetBlue). Europe has seen similar growth, with dominant LCCs such as easyJet and Ryanair.
(5) The end of supersonic transportation - Concorde. I realize that this may not seem important to some people, but I think it is very significant as there are no new supersonic transports on the near horizon. Economics won and the airline world took a technological step backward when Concorde flights ended in 2003.
(6) Two-engines for the long-haul. A quick look at what airlines were flying in 1989 vs. today is astonishing. Trans-atlantic flights were almost all 3- or 4-engined aircraft. Ditto for trans-Pacific flights. The 767, followed by the 777, A330, and even the 757, allowed airlines to efficiently fly to markets that were too big for the 747s. It literally opened up dozens of new airports to intercontinental service for the first time. The 767 accounts for easily the most trans-Atlantic flights in today's world.
(7) Increase in cabin amenities and in-flight entertainment. In 1989, most long-haul flights were punctuated by old-style film projectors and a constantly replaying music selection. The mid-90s saw the PTV quickly become the choice of airline passengers, and with it came a selection of what to watch (or play). This has even trickled down into some LCCs and on shorter flights; it is now possible to watch satellite TV
, use the internet and receive emails all at 39,000 feet. Also, airline seats are much more advanced today, even in economy class. Most airlines have more pitch and more comfort today; the consumer demands it!
(8) SARS. Thankfully, the epidemic seems to have subsided for now. But it took a dramatic toll on airlines worldwide, especially in Asia. It was a disease that seemingly could be spread around the stagnant air of an airline cabin and passengers chose not to fly because of it, much like terrorism. It could have killed some airlines too. SARS maybe gone (for good, I hope), but the vulnerability of a communicable disease spreading through an airline cabin definitely exists.
These are my selections. There are probably more that I am forgetting, and the order is always up for debate, but I think this sort of sums up the last 15 years. Think of how different this industry might look 15 years from now....