In theory, all the systems show the same data; in practice, however, they get a little out of sync with each other. If you're looking for seats on a sold-out flight, an airline's home system is most likely to have that last, elusive seat. If you're looking for the lowest fare to somewhere, check all four systems because a fare that's marked as sold out on one system often mysteriously reappears on another system. Some airlines have rules about flight segments that are not supposed to be sold together even though they're all available, and at least once I got a cheap US Airways ticket on Expedia, which didn't know about all the US Airways rules even though I couldn't get it on their own site or Travelocity which did know about them. On the other hand, many airlines have available some special deals that are only on their own Web sites and maybe a few of the online agencies. Confused? You should be. We are.
Passengers are subject to much more extensive screening than in the past, including screening of checked baggage at check-in time, and, according to news reports pat downs that approach groping. Airlines recommend arriving at least an hour earlier than before. In my experience the extra delay is rarely more than 15 minutes, even with the extra baggage screening, although I usually fly out of smaller airports, not big hubs where you can get the killer two hour lines. The TSA has handed back screening at a surprising number of airports to private contractors, all of whom wear outfits intended to look like TSA uniforms. There is remarkable inconsistency in procedures from one airport to another, particularly with respect to your shoes, is worse than ever. Don't put your shoes in a bin, do put your shoes in a bin, and they all insist very loudly that whatever their rule is has always been the rule everywhere. A variety of extra cost "trusted traveller" plans may allow people to get through the screening faster, or may just involve waiting in a different line. The TSA makes no promises. If you don't want to go through the X-ray machines, whose safety is nowhere near as clear as the TSA would like you to believe, you can get a light body massage instead. They have a web site with estimated wait times based on averages in previous months, not real time numbers.
Travel dates back to antiquity where wealthy Greeks and Romans would travel for leisure to their summer homes and villas in cities such as Pompeii and Baiae. While early travel tended to be slower, more dangerous, and more dominated by trade and migration, cultural and technological advances over many years have tended to mean that travel has become easier and more accessible. Mankind has come a long way in transportation since Christopher Columbus sailed to the new world from Spain in 1492, an expedition which took over 10 weeks to arrive at the final destination; to the 21st century where aircraft allow travel from Spain to the United States overnight.