Four giant airline computer systems in the United States handle nearly all the airline reservations in the country. (They're known as CRSs, for computer reservations systems, or more often now GDS for global distribution systems.) Although each airline has a ``home'' CRS, the systems are all interlinked so that you can, with few exceptions, buy tickets for any airline from any CRS. The dominant systems in the U.S. are Sabre (home to American and US Airways), Galileo (home to United), Worldspan (home to Delta, Northwest), and Amadeus (many European lines.) The company that owned Galileo and Orbitz recently bought Worldspan, so the two GDS will presumably be merged. Many of the low-price start-up airlines don't participate in any of these systems but have their own Web sites where you can check flights and buy tickets. Southwest, the largest and oldest of the low-price airlines, doesn't participate, either. Southwest's web site gets car and hotel info from Galileo, but the info seems not to flow the other way. Orbitz one of the big three online travel agencies, runs its own system which is "direct connect" linked directly to many of the airlines.
Avoid walking after dark, especially alone, and avoid deserted or under-populated areas. Only go to bars and nightclubs in a group and avoid separating from the group. Avoid excessive alcohol consumption, and do not accept invitations or rides from strangers or recent acquaintances, as these can make you a more vulnerable target for criminals. In cases of sexual assault, police authorities will order a medical examination.
Wait times are assessed automatically as follows: on departure, the passenger’s boarding pass is scanned when he/she enters the queue, then again just before he/she begins the individual screening process and, on arrival, when the passenger lines up in the visitors or residents queue in the primary inspection area and again when he/she exits from the area behind the customs officers’ posts.
Cases of sexual assault against female travellers have been reported. Always travel in groups and avoid isolated areas, including unsupervised beaches, especially at night. Never leave food or drinks unattended or in the care of strangers. Be wary of accepting snacks, beverages, gum or cigarettes from new acquaintances, as they may contain drugs that could put you at risk of sexual assault.
The first step to an international trip is to read our Traveler’s Checklist to find out things to consider before you go. Pay special attention to our safety and security information and assess for yourself the risk of traveling to a particular country or region. Some U.S. citizens with special considerations – such as students, women, and LGBTI travelers – may face additional challenges when abroad. If you do decide to travel, make a plan for what to do if something goes wrong overseas. 
Other changes include: some airports have stopped curb-side baggage check, anything vaguely resembling a knife or lighter may or may not be confiscated (although lighters suddenly stopped being dangerous a year ago), you're sometimes only allowed one carry-on plus a purse, briefcase, diaper bag or the like, non-passengers aren't allowed past security, all passengers must have a document that looks like a boarding pass at most airports to get past security, you may have to put your toothpaste and shampoo in a baggie that may have to be a one quart size, some parking areas close to terminals are closed. But check-in clerks no longer ask you whether you packed your own suitcase.
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