When did you last fly with Southwest Air Fast Express or Universal Aviation or Colonial Air Transport? Have you ever been a passenger with Instone Air Line, British Marine Air Navigation or Handley Page Air Transport? How about Air Orient, Air Union, CIDNA or SGTA?

All of these airlines still exist, in a way — though their names are long forgotten. They merged to form bigger airlines. The first three were among 82 small carriers that came together in 1930 to create American Airways, subsequently American Airlines. The next three were absorbed into Imperial Airways, now British Airways. And the final batch were among the airlines that formed Air France.

American Airlines © Redwood8 | Dreamstime.com

Airline mergers have been a fact of life since the beginning of commercial aviation. Flying requires the subversion of one of the governing forces of physics: gravity. But it is economic forces that all too often bring fledgling airlines down to Earth with a bump. As the old saying goes, “It’s easy to make a small fortune in aviation. Just start with a large fortune.”

Few industries are vulnerable to so many variable factors. An airline is not just dependent on finding enough people to travel on a particular route at a particular time. Its fortunes are tied to the fluctuations in the price of fuel, the weather, volcanic eruptions, local and global security issues and to startup, low-cost rivals undercutting their fares.

Competition, leading to a shift in the behavior of the traveling public, helps keep airfares down. In the decade since 2004, domestic airfares in the United States fell by 0.5 percent. Since 1978, average global airfares have halved in real terms.

Good news for passengers has been terrible news for many airlines. America’s de facto flag carrier, Pan Am, ceased operations in 1991. In the past decade and a half, some of the biggest surviving airlines teetered on the edge of terminal insolvency: American Airlines, US Airways, Delta Air Lines, Northwest and United Airlines all spent time under Chapter 11 bankruptcy. Forty-seven smaller American carriers disappeared permanently, and the national airlines of Switzerland, Belgium, Greece, Cyprus, Bulgaria, Brazil, Venezuela, Ghana and Malawi, among others, bit the dust.

Star Alliance © Jiri Senohrabek | Dreamstime.com

Airline executives face the challenge of finding some way of bringing stability to this intrinsically unstable industry. The establishment of global airline alliances offered one solution. Between 1997 and 2000, three heavyweight alliances emerged: Star Alliance, oneworld and SkyTeam. With a current total of 62 member airlines, these three alliances carry 1.7 billion passengers each year, half a billion more than all of the world’s other airlines combined.

Joining an alliance offers an individual airline immediate benefits. Shared booking, maintenance and baggage facilities help lower the day-to-day costs. For the traveler, it becomes possible to ply intercontinental routes seamlessly on codeshare flights operated by different carriers within a particular alliance.

And yet even under the protective umbrella of the big three alliances, the early years of the 21st century proved to be some of the most challenging in aviation history. It was clear the industry needed to find a new model, and so began the biggest round of airline mergers since the era of the pioneers, when the pilots wore goggles and wooden propellers powered the planes.

Southwest Airlines © Nicholas Burningham | Dreamstime.com

At the turn of the millennium, there were 10 major airlines in the United States. Now there are four. TWA, America West and US Airways merged with American Airlines. Delta Air Lines and Northwest have come together, as have United and Continental, and Southwest and AirTran. These four mega airlines now account for 80 percent of all domestic air traffic in the United States.

The rate of change has been unprecedented, bringing with it major upheaval for travelers as carriers amend frequent-flyer programs, scrap unprofitable routes and switch terminals in major hub airports.

The immediate aftermath of a merger is seldom smooth. In the wake of the union of US Airways and America West in 2007, passenger complaints doubled. A 60 percent surge in complaints occurred after United Airlines merged with Continental in 2010.

Add to that the more prosaic issues of blending the corporate cultures of different airlines. Not all the changes are embraced by the employees, leading to friction and, sometimes, to strike action.

The aftermath of the United-Continental merger was beset with problems. On-time performance dropped markedly and the rate of lost bags increased. More catastrophically, computer glitches periodically disabled the reservations system and on occasion brought all operations worldwide to a standstill. By September 2012, United’s on-time arrival rate dropped to just 77.5 percent, the lowest among the major American carriers.

It is only now, after nearly five years, that we can begin to deduce the long-term impact of the United-Continental merger. For the expanded company, operating profits in 2014 rose by 86 percent, though write-downs, fuel contracts and other one-off costs resulted in a hefty overall loss.

For passengers, the years of disruption have finally begun to translate into efficiency, though at a price. Average per-mile fares rose by 1.3 percent, and ancillary fees (including checked bags and the purchase of extra-legroom seats) increased by 9.7 percent to $22 per passenger.

The merger of American Airlines and US Airways, which was consummated in December 2013, represents a corporate marriage on an even greater scale, resulting in the world’s largest airline. Passengers have been braced for a repetition of the chaos that followed the much smaller merger of US Airways and America West, though CEO Doug Parker, keen to avoid the mistakes of the past, is pursuing a flexible timetable for full integration. “The targets are not set in stone,” he said late last year. “If we’re not ready, we won’t go.”

Delta Air Lines © Boarding1now | Dreamstime.com

For regular passengers, one of the biggest bones of contention after a merger is what happens to the frequent-flyer program. Both United and Delta introduced new systems to reward flyers for dollars spent rather than miles flown. It’s a switch which, according to a study by PricewaterhouseCoopers, resulted in 45 percent of passengers losing points.

When US Airways’ Dividend Miles program was absorbed into American’s AAdvantage plan in April, the expanded frequent-flyer program continued to reward points on a miles-flown basis, though American hasn’t ruled out changes in the future.

The consolidation of carriers in the United States is being repeated elsewhere in the world. In Europe, the first big merger — between Air France and the Dutch national carrier KLM — went through in 2004. Both airlines chose to keep their names, with the group headquarters in Paris.

KLM © Richair | Dreamstime.com

British Airways spent many years looking for a suitable match. In the 1990s there was a long and public courtship with American Airlines. The proposed union was vehemently opposed by Sir Richard Branson’s Virgin Atlantic. Some Virgin Atlantic planes were painted with the slogan, “No Way BA/AA.”

When that merger fell through, British Airways turned its attention to KLM. That deal ultimately languished due to political and regulatory obstacles, and KLM subsequently fell into the arms of Air France. At last, in 2011, British Airways successfully found a partner when it formalized a merger with the Spanish carrier Iberia.

British Airways © Tommy Beattie | Dreamstime.com

The implosion of the Spanish economy made for a rocky start to the marriage, but under the official name of the International Airlines Group, the merged airlines announced profits of nearly $1 billion for 2014. The thriving group has now set its sights on a merger with the Irish carrier Aer Lingus.

According to many industry analysts, the trend for airline mergers is far from over. Seattle-based Alaska Airlines is often mentioned as a potential merger target, with both Delta and American Airlines seen as potential suitors.

The low-cost carrier JetBlue previously distanced itself from merger speculation, though some industry insiders suggest the next bout of consolidation could be among lowcost airlines. With German carrier Lufthansa set to sell its 15 percent stake in JetBlue, a new corporate direction could be in the cards.

Of all the changes on the horizon for the airline industry, perhaps the greatest is the rapid rise of the Asian market. China is expected to overtake the United States as the world’s largest passenger market within the next 15 years. The growth of Chinese airlines will continue apace, with the real prospect they will ultimately be involved in a flurry of international acquisitions and mergers.

By its very nature, aviation is an industry that never sits still. Global annual passenger numbers are expected to more than double within the next 20 years, to 7.3 billion. The industry will continue to evolve in order to keep pace.

When we look at airport departure boards, we are witnessing a snapshot in time. Look at the same boards five years from now: Which airline names will still be there, and which will have gone forever?