Five most significant changes in air travel since 9/11

— -- It's been 34 years since the airline industry was deregulated, but in many ways the terrorist attacks of 9/11 were a much more significant watershed for passengers. For a variety of reasons, flying has been completely remade over the last ten years, and we've all felt the effects.

I've been immersed in the industry for 27 years, first as an airline employee, then as a journalist and passenger advocate. But in researching my latest book ( Attention All Passengers: The Airlines' Dangerous Descentand How to Reclaim Our Skies), I was struck by just how much has changed in a relatively short time.

Differences aloft

Here are what I believe to be the five most significant changes for airline passengers in recent years.

•Fees. The airlines call it "ancillary revenue." You may be among the millions who call it "nickel-and-diming." But there's little doubt the influx of dozens of fees for everything from checking a bag to selecting a seat has transformed flying. They also represent effective (some would say hidden) airfare increases. In survey after survey, add-on fees are the top passenger gripe, as Consumer Reports found last year. And it certainly isn't coincidental that Southwest (first two bags free) and JetBlue (first bag free) outrank all other domestic carriers in such surveys.

•Shrinking industry. According to the industry trade association Airlines for America, there have been 14 major mergers and acquisitions among domestic carriers since 2001. I've written at length about how I perceive such consolidation is harmful to consumers, communities and airline employees. But the loss of such major brands as TWA, America West, Northwest, Continental and now possibly American -- which has suitors for a potential merger after recently declaring bankruptcy -- has completely reshaped the U.S. airline business, leaving the country with just four "legacy" carriers: United, Delta, US Airways and—for now—American.

•Shrinking workforce. Tens of thousands of full-time airline employees have been laid off, furloughed or "downsized" since 9/11, as more and more aviation jobs have been converted to part-time status or outsourced to companies located both here and abroad. For passengers, this may mean uniformed personnel interacting with the public are not in fact airline employees and do not have the same level of training and expertise. It also could mean that outsourced aircraft maintenance work is being performed at facilities with unlicensed mechanics and without the same level of federal oversight.