American Airlines  is one of the largest airlines in the United States and a founding member of the Oneworld airline alliance. It is the predominant carrier between North America and Latin America and has flights from the US to Western Europe, China, Korea, and Japan. On December 9, 2013 American Airlines and US Airways merged to become the World's Largest Airline.
NOTE: The following list ONLY INCLUDES the hubs and Focus cities owned by American Airlines. This list does not included US Airways. With the merger now completed, all of US Airways Hubs are now owned by American Airlines.
Dallas/Fort Worth (IATA: DFW) is AA's official headquarters and largest hub, with flights to destinations throughout the AA network, including the longest 747 flight from Sydney, Australia on Qantas. Although most of DFW's passengers are connecting, the airport was designed to be most convenient for locals: gates are very close to ticketing and baggage claim, but very far from each other. Fortunately, DFW has a new, fast and clean people mover system which makes two stops in each terminal. The international terminal (Terminal D) is the newest terminal in the airport serving for American Airlines (domestic & international flights) and other foreign carriers, while the original 4 terminals are currently under a $2 billion makeover. American Airlines use all terminals EXCEPT Terminal E.
Chicago (IATA: ORD) is also an important hub for AA, handling flights across the US and to Europe and Asia. It is particularly susceptible to delays and cancellations in the winter, which can be good if you don't mind getting bumped and compensated, but can be bad if you're flying on a time-sensitive schedule. However, Chicago is the only AA station with service to Beijing and many European destinations.
Miami (IATA: MIA) is AA's main north-south hub: if you're headed to Latin America, you will probably transit through either Miami or DFW. AA's terminal at MIA has been under construction for several years, so you may be in a brand-new part (concourse A and much of concourse D) or a very old part (concourse C, E and part of concourse D). Check-in, security, customs and immigration at MIA tend to be a hassle, so plan ahead and allot yourself extra time when departing or connecting through the airport. It is also a major connection point
New York (IATA: NYC metropolitan/all airports) is a major market for AA, with three airports all serviced by American.
The main airport, John F Kennedy International Terminal 8 (IATA: JFK) handles a number of transatlantic connections. It's also the major east coast connection point to OneWorld partner airlines for both transatlantic and transpacific service. The brand new terminal 8 is fully functional and now handling all of AA's domestic and international traffic.
LaGuardia (IATA: LGA) is closer in to Manhattan by cab, and has both incoming flights from the DFW and ORD hubs as well as acting as a local hub for some short-haul regional flights in the northeast.
Los Angeles Terminal 4 (IATA: LAX) is smaller hub on the west coast; most flights to smaller west-coast destinations not large enough to be served directly out of Dallas or Chicago will connect through Los Angeles. Also, there is transatlantic service to London, transpacific service to Tokyo and Shanghai, and it is a major connection point to transpacific service with OneWorld partners of JAL, Cathay Pacific & Qantas; transatlantic service on British Airways; and LAN/LAN Peru to South America. American Airlines operates from Terminal 4 where it is equipped with customs halls for use of American Airlines' passengers arriving from outside the U.S.
San Francisco (IATA: SFO) is not a hub for American; however, it has some non-stop service to major east coast cities and is a major connecting point to transpacific service on OneWorld partners JAL, Cathay Pacific, and also has transatlantic service on British Airways and South America service on LAN.
NOTE:The Aircrafts listed are from AA and it does NOT INCLUDE the Pre-Merger US Airways.
Boeing 777s are used on all transpacific routes, flights to London, Frankfurt, Madrid, and on flights to South America, such as Buenos Aires and Sao Paulo. Domestic routes include Chicago-Dallas-Forth Worth and Los Angeles-Miami. These are the only three-class aircraft in AA's fleet (besides the handful of 767-200's described below). All of the Boeing 777 aircraft are equiped with the "Flagship Suites," for First Class seating. These are enclosed seats that offer a fully-flat bed, personal on-demand video enterntainment, lots of privacy and large workspace. "Flagship Suites" are similar to the first class suites on British Airways and many Asian carriers. Business Class features angled-lie flat "Next-Generation Business Class" (NGBC) seats, which are nearly identical to those found on found on the AA Boeing 767's. All seats come with personal on-demand video as well as a large work table.
Boeing 767-300s are used on many long-range routes to Europe and South America, and a few long-haul domestic routes. They are two-class aircraft. Business class comes with lie-flat NGBC seats, and video on demand, coach just has overhead video screens.
Boeing 767-200s provide three-class service on flights from JFK to Los Angeles and San Francisco as well as JFK-Miami. These have a much older first class cabin than other AA planes, although it is quite comfortable. First Class is currently being updated with new fully-flat seats.
Boeing 757s are used on many medium to long-range routes, particularly to and from Miami and the Northeast and Central America, and for a handful of transatlantic flights as well. They have overhead televisions but no personal video. These aircraft are currently being updated with new interiors, featuring LCD screens and new seats. Aircraft operating transatlantic routes have been converted so that business class comes with lie-flat NGBC seats, and video on demand, coach just has overhead video screens.
Boeing 737s are increasingly used short and medium range flights, and with new purchases should be the mainstay of the fleet in the next few years. These aircraft have overhead video screens and feature similar First Class seats to those in the MD-80's. There are a mix of older and newer 737s, with the newer (and updated models) having a much newer (and generally more pleasant) interior but slightly worse leg room; you can tell the age of the plane via the seat map -- if rows 13 and 14 are the over-wing exits, it's an older interior, while if rows 14 and 15 are the exits, it is either new or refurbished interior.
McDonnell Douglas MD-80s are being phased out, but remain the mainstay of AA's medium-range fleet, and you are exceedingly likely to board one (or two) if you are connecting in Dallas or Chicago. Economy class on the MD-80 is the most spacious economy in the AA fleet, with an extra inch of seat pitch and width in comparison to most other AA aircraft. Seating is five-abreast (2-3), meaning you are less likely to get a middle seat. First class on an MD-80 features large, reclining seats. However, there is no in-flight entertainment on the MD-80s. Because the engines are at the back of the aircraft, first class is very quiet and the back rows are very loud.
'"Airbus 319, 320'" will begin service in September 2013.
American Eagle, which operates AA's feeder flights, mainly uses single-class Embraer regional jets, along with some Canadair regional jets (CRJ-700), and a handful of tiny Saab 340s and ATR's based mainly in Miami
American, prior to its reorganization, announced a major fleet renewal. So far it appears to be continuing on schedule, with new 737s coming live, and the new 777-300ER (the present models being -200ER) entering service late in 2012. American is expected to start flying the Airbus A320 and 787 within the next few years as part of this renewal effort, and to finish retiring the MD80.
AAdvantage members earn miles on all Oneworld carriers (although in some cases, only in limited fare codes), as well as, Air Pacific (Fiji), Air Tahiti Nui, Alaska Airlines, El Al, Gulf Air, Gol (Brazil), Hawaiian Airlines, Jet Airways, and select routes on JetBlue. For the current list of Advantage Mileage Earning Airlines refer to here: 
As of late 2010 (with anti-trust approval earlier in the year and the first major changes effective 10/1), beyond the OneWorld membership, American Airlines is part of a new Joint Business Arrangement with British Airways and Iberia, including increased numbers of code-share flights and cooperation on transatlantic flights (including a removal of the prior rule of no mile-earning on transatlantic BA flights.)
A similar agreement for transpacific flights went into effect with Japan Airlines in April 2011, and a (separate) similar agreement went into effect with with Qantas in May 2012.
American has two basic types of its own award tickets: MileSAAver, which is subject to blackout dates and capacity restrictions, and AAnytime, which is not subject to blackout dates or capacity restrictions.
AAnytime tickets generally cost twice as many miles as MileSAAver tickets. Some international markets have "peak" and "off-peak" mile costs for economy class travel which skew this basic formula slightly.
AAdvantage miles can also be redeemed for point-to-point "All Partners" awards to a given destination, which can include a mix of AA and partner flights, including some which are non-Oneworld airlines.
Awards on American flights, as well as some partner flights (as of 8/2012, British Airways, Iberia and Qantas) can been checked and redeemed via the corporate website, while other partners can only be booked via telephone agents.
An informal Wall Street Journal study in 2007 concluded that American was one of the easiest US major airlines on which to redeem miles for free travel.
AAdvantage miles can also be redeemed for car rentals and hotel stays.
AAdvantage elite status is determined by the number of miles or segments you fly on an AA, AA codeshare, Alaska Airlines or mile-earning Oneworld flight. You can also earn status based on your accrued elite qualifying points: you get 1 point per mile traveled on most discounted economy tickets, 1.5 points per mile on full-fare economy and premium class tickets, and 0.5 points per mile on deeply discounted economy tickets. The basic tiers are: 
Gold (25,000 miles/points or 30 segments) - Oneworld Ruby
Platinum (50,000 miles/points or 60 segments) - Oneworld Sapphire
Executive Platinum (100,000 miles/points or 100 segments) - Oneworld Emerald
Elite status members are generally given a "soft landing" if they fail to requalify; Platinum to Gold, etc. Most years, the American Airlines will also offer members with elite status who fell short of the total (but who did at least some flying in the past year; the exact threshold is not publicly announced) a chance to buy status for another year. This generally cannot be repeated two years in a row.
AAdvantage is unique among frequent flyer programs in its challenge program. A passenger can earn Gold or Platinum status by calling AAdvantage, asking to take the challenge, and then racking up a certain number of elite qualifying points (not miles!) within a certain period of time; there is a small fee for enrollment ($240 for Platinum, $120 for Gold, as of August 2012) which is not refunded if the challenge is not completed. The requirements have been stable at 5,000 points in 3 months are presently required for the Gold challenge and 10,000 points for the Platinum challenge. 
It should also be noted that a passenger can only attempt a status challenge when they do not hold that status -- it is intended to bring new people into elite status, not as a method of retaining elite status. So while you can make Platinum with some trans-pacific rounds trips in economy class (or virtually any in business or higher), you will have to follow that up with much more mileage in order to retain your status for more than a year.
AA's main lounge is called the Admirals Club. 
Membership costs $500 for the first year and $450 each year thereafter; you can also buy membership with AAdvantage miles, and obtain discounts based on your AAdvantage elite status. There is a discount for a married couple joining/renewing at the same time.
Oneworld Sapphire and Emerald members can use Admirals Clubs when travelling on a Oneworld itinerary that day; AAdvantage Platinum and Executive Platinum members can only take advantage of this when traveling on a same day international itinerary.
American also has a special first class lounge, called the Flagship Lounge, in Chicago, Los Angeles, Miami, London-Heathrow and New York - John F. Kennedy International Airport. Access to the Flagship Lounge is available if you are traveling in first class to/from Europe, Asia, Central America, South America or Mexico City, or if you are traveling in first class on certain coast-to-coast transcontinental flights (in the case of LAX or SFO), or if you are an Executive Platinum/Oneworld Emerald member and otherwise eligible to use the Admirals Club. For first class transcons, you must be booked in F or Z inventory, but this does include AAdvantage awards. For international 3-cabin flights, you must be in First Class, but it doesn't matter how you got there.
London Heathrow also has an Arrivals Lounge open to all arriving first and business class passengers. Economy passengers can also use the lounge by paying US$90 plus VAT at the door. The lounge has showers, drinks, gym equipment and a business center.
This is a usable article. It touches on all the major areas of the topic. An adventurous person could use this article, but please plunge forward and help it grow!