MIDWEST DESTINATIONS (IOWA, WISCONSIN, DAKOTAS, ETC) - American Airlines or United Airlines though Chicago O'Hare (ORD) or Delta Airlines though Detroit (DTW). Delta has drasticaly reduced its hub operations at Cincinnati (CVG) after the Northwest merger but there are still many local midwest connections through CVG and, though expensive, many more through DTW which was picked up from Northwest. Delta also operates a smaller hub at MSP but in most cases you will do better connecting through DTW. Also consider that Airtran/Southwest are offering some service through Chicago Midway (MDW) and Milwaukee (MKE).
SOUTHEAST DESTINATIONS (CAROLINAS, MISSISSIPPI, ALABAMA, ETC) - US Airways through Charlotte (CLT), Delta through Atlanta (ATL). Miami (MIA) is American's Southeast hub (and a large one) but it is usually not practical to fly to the bottom corner of the continent, for flights going inland. If you prefer to fly American and are headed to the Southeast, go through DFW or JFK. Airtran also maintains its hub at Atlanta Hartsfield (ATL)
LATIN AMERICA, CARIBBEAN, SOUTH AMERICA - American Airlines through Miami (MIA), Continental Airlines through Houston (IAH) or Delta Airlines through Atlanta Hartsfield (ATL)
SOUTHWEST DESTINATIONS - American Airlines through Dallas/Ft Worth (DFW), US Airways or Southwest Airlines though Las Vegas (LAS), Delta through Salt Lake City (SLC) or United Airlines or Frontier Airlines through Denver (DEN).
CALIFORNIA DESTINATIONS - American Airlines or JetBlue through Los Angeles (LAX). United Airlines through SFO (or to a lesser degree, through LAX).
ASIA - Fly though Toronto (YYZ), Seattle (SEA), Portland (PDX) which by the way is a very well liked airport if the route works for you, Los Angeles (LAX), Chicago (ORD), San Francisco (SFO) or sometimes New York (JFK)
EUROPE - JFK is by far and away the largest hub. There are also significant flights to Europe from Chicago (ORD), Philadelphia (PHL), Washington Dulles (IAD) and Atlanta (ATL).
Note that you can fly almost anywhere in the world through New York's JFK airport and so many Boston flights are routed through JFK. There are advantages such as the quick flight, the large number of flights (which means that if you miss your connection there is often another one) and the wealth of places that you can go through JFK. Although JFK is a zoo, if you leave amply connection time, it is usually just fine to fly through. However, from a technical standpoint, flying through JFK often uses up alot of time to not get very far. You see short flights, as is the case between Boston and New York, fly a slower speeds. The time that it takes just to climb after take off and descend before landing is very similar, regardless of the flight. Flying through JFK insures that you spend alot of time just going up and then coming down, rather than gaining any ground towards your destination. For this reason, I often avoid flying through JFK, opting instead for a connecting flight that gains me some distance. Additionally, winter weather will plague places like NY and Chicago. So, give this some consideration if you are flying somewhere warmer. If your final destination is Mobile, AL for example, and you connect in NY, snow can slow you down. If you connect in Atlanta or Charlotte, you will have no such risk.
On the flip side, many flights routed through JFK are the least expensive way to go. The sheer volume of traffic through JFK can often provide you the most competitive rate.
OTHER AIRLINE HUBS:
FRONTIER AIRLINES - Headquartered in Denver and servicing Kansas City and Milwaukee, Frontier consists of the merged Midwest Airways as well and services the central/Rockie areas as well as having flights to Mexico and Costa Rica for vacationers.
Lets just start calling Boston a hub for Jetblue. Over the past five years, Jetblue has surpassed all other airlines at Logan Airport, now offering daily non-stops to more destinations than any one airline has ever offered from Boston at one time. Advantages abound such as reasonable fares, liberal change policies, comfortable planes with DIRECT TV and a seemingly greater commitment to flying on time. Jetblue seems to fly everywhere, an increasing advantage as airline delays make connecting at hubs a tricky business. From Boston, Jetblue flies directly to so many cities that for domestic travel you are starting to need fewer and fewer other choices. Jetblue was first to fly directly to Jacksonville for example, has pretty much taken over Delta's long monopolized Florida routes such as Ft Lauderdale, West Palm, Tampa and Ft. Myers (yes they fly to Orlando too but, who doesn't?). They have direct flights now to San Diego and Los Angeles, domain that was always owned by American Airlines. And recently, with an almost orgasmic response from the business community, they have added flights to Newark (EWR) a route which Continental seemed to have bulletproof domination over and Dallas/Ft Worth (DFW) a route which was monopolized by American. Jetblue has also added some international happy destinations such as Cancun and St Martin, has resurrected American Airlines abandoned Boston to San Juan route (nos gustamos!). And while all of these routes are welcomed by Bostonians who are tired of connecting through nightmare hubs like O'Hare and Hartsfield, one wonders how it is that Jetblue can just keep adding routes, especially in recessionary times. Lets hope that Jetblue has a good plan to keep these routes strong, so that we can keep this happy marriage for a long time. Update: See how Jetblue is starting to evolve into Boston's first hub airline.
In someways, Southwest Airlines changed how Bostonian's flew. The idea of flying out of any airport other than Logan was absurd for any New Englander other than those living in CT and Western MA. Boston was the gateway, period and there were no other choices. Then along came Southwest Airline, which began offering less expensive, ultra flexible flights to popular destinations from Manchester NH (MHT) and Providence Rhode Island's TF GREEN (PVD). With a heavy focus on their Baltimore hub (BWI) and flights to Florida, Southwest drew Greater Boston travellers to these smaller airports where parking was cheaper and easier and the whole airport experience was just less complex. I would park for flighs from Manchester, walk across the garage into security lines and be at my gate in 15 minutes. Not only did Southwest open up these airports for broader business, they changed travellers focus on the major airport only because although the drive may have been longer, the waits were shorter and the experience far more tolerable. On the flip side however, were the problems created when bad weather days or days when air traffic control was bottlenecked, caused flights to these smaller airports to be cancelled. In such cases, you may just miss the one flight back home that day and that creates problems. Flying to Chicago from Boston may not be the world's greatest experience, but if you miss a flight, you have lots of later flights to choose from.
The past year has brought changes though for Southwest and the outlying New England airports. The combination of Jetblue's entrance into the market and the addition of some Southwest flights from Logan, may eventually bring a close to the migration of Boston Area travellers to the smaller airports. Manchester in particular is vulnerable because it does not have quite the substantial population that Providence does to support its own airport, just with its local residents. Still, Manchester is a wonderful airport and the NH Department of Transportation is one of the finest in the nation in designing good roads and easy access.
Southwest has currently picked up flights to St. Louis (STL), to replace American's departed service to that hub and Baltimore (BWI) flights of course as that is Southwest's east coast hub. Recenty, Southwest exited the Boston to PHL route. Read here for more info.
Dallas original airport is named Love Field (DAL). In the seventies, as air travel was expanding, it was felt that Love Field would not be able to handle the air traffic for the large Dallas/Ft Worth metropolis which is home to more than six million people. So the quest was out to build a new airport which could handle the expansion and thus came the birth of Dallas/Ft. Worth International Airport (DFW) which also became the home and largest hub for the gigantic American Airlines. Airlines were all to support the new airport, but Southwest did not want to move because they liked Love's location closer to where people lived (at the time). So, Southwest (and also Braniff airines) stayed at Love Field. However, Dallas wanted full support for DFW and didn't want to have to operate a smaller airport that was not in full use, so Ft. Worth Congressman Jim Wright, in 1979, wrote the WRIGHT AMMENDMENT which restricted flights out of Dallas Love Field to either Texas destinations or to one of the four adjacent states. The Wright Ammendment helped DFW to grow to the monolith that it is today as the eighth busiest airport in the world according to passenger traffic (and number four if you count aircraft movements since DFW is a very large cargo hub as well). But the restriction also crippled Southwest's business out of DAL and has been a source of debate and controversy ever since.
The Wright Ammendment has in principle been repealed but the changes will not take affect until 2014, before which time there is still plenty of room to reopen the controversy.