So you want to plan the trip on your own? This article tells you all you need to know to research and book the perfect flight.

Booking your flight

With the introduction of codesharing — one carrier selling flights as its own on another carrier — customers now enjoy more travel options and an easier time making flight arrangements. Chances are, you can call your favorite airline and come up with a plan that flies you from just about anywhere in the United States to just about anywhere in Europe. Listed in the Appendix are the phone numbers and Web sites for all the major U.S. and European airlines that offer direct flights from North America to Europe. In these days of airline alliances, widespread codesharing, and carrier consolidation, it barely seems to matter which airline you call to make your booking. Chances are, their interlocking partnerships will ensure you can flit from your hometown to your European destination on any combination of carriers, foreign or domestic, and any one of them can arrange this for you.

You may have to travel first to a U.S. hub, such as New York, in order to pick up a direct flight to your destination, and to reach smaller European cities you’ll probably be routed through a major European hub such as Paris or Frankfurt.

Shopping for the best airfare

Competition among the major U.S. airlines is unlike that of any other industry. Every airline offers virtually the same product (basically, a coach seat is a coach seat is a . . .), yet prices can vary by hundreds of dollars.

Business travelers who need the flexibility to buy their tickets at the last minute and change their itineraries at a moment’s notice — and who want to get home before the weekend — pay (or at least their companies pay) the premium rate, known as the full fare. But if you can book your ticket far in advance, stay over Saturday night, and are willing to travel midweek (Tuesday, Wednesday, or Thursday), you can qualify for the least expensive price — usually a fraction of the full fare. On most flights, even the shortest hops within the United States, the full fare is close to $1,000 or more, but a 7- or 14-day advance-purchase ticket may cost less than half of that amount. Obviously, planning ahead pays. The airlines also periodically hold sales in which they lower the prices on their most popular routes. These fares have advance-purchase requirements and date-of-travel restrictions, but you can’t beat the prices. As you plan your vacation, keep your eyes open for these sales, which tend to take place in seasons of low travel volume — for Europe that’s generally September 15 through June 14. You almost never see a sale around the peak summer-vacation months of July and August, or around Thanksgiving or Christmas, when many people fly regardless of the fare they have to pay — though this is obviously less true if you can get a direct flight to Europe from your home airport (most folks travel domestically for the holidays). Often, flying into Europe’s major cities (usually London and Paris) brings the price of a ticket down. Also, look into purchasing an open-jaw plane ticket, one that allows you to fly into one European city and depart from another — say, flying into London but out of Madrid on your way home. Open-jaw tickets can sometimes be a more expensive option — although usually no more than half the price of a round-trip ticket to London plus half the round-trip Madrid fare — but it’s a wonderful way to keep your itinerary flexible, and you don’t have to backtrack to the first city on your trip.

Consolidators, also known as bucket shops, are great sources for international tickets. Start by looking in Sunday newspaper travel sections; U.S. travelers should focus on the New York Times, Los Angeles Times, and Miami Herald. For less-developed destinations, small travel agents who cater to immigrant communities in large cities often have the best deals.

Bucket-shop tickets are usually nonrefundable or rigged with stiff cancellation penalties, often as high as 50 to 75 percent of the ticket price, and some put you on charter airlines with questionable safety records. Some reliable consolidators include the following:

- AutoEurope (888-223-5555; www.autoeurope.com)
- Cheap Tickets (800-377-1000; www.cheaptickets.com)
- STA Travel (800-781-4040; www.statravel.com)
- Lowestfare.com (866-210-3289; www.lowestfare.com)
- ELTExpress (800-TRAV-800; www.flights.com)
- Air Tickets Direct (800-778-3447; www.airtickets direct.com)

Booking your flight online

The “big three” online travel agencies, Expedia (www.expedia.com), Travelocity (www.travelocity.com), and Orbitz (www.orbitz.com) sell most of the air tickets bought on the Internet. (Canadian travelers should try www.expedia.ca and www.travelocity.ca; U.K. residents can go for expedia.co.uk and opodo.co.uk.). Each has different business deals with the airlines and may offer different fares on the same flights, so shopping around is wise. Expedia and Travelocity will also send you an e-mail notification when a cheap fare becomes available to your favorite destination.

Of the smaller travel agency Web sites, SideStep (www.sidestep.com) receives good reviews from users. It’s a browser add-on (PCs only) that purports to “search 140 sites at once,” but in reality only beats competitors’ fares as often as other sites do. Also check out Cheapflights.com — a fantastic meta-search engine that will give you the going rate for any destination from the airlines sites, the booking engines like Expedia, and the major consolidators.

Great last-minute deals are available through free weekly e-mail services provided directly by the airlines. Most of these deals are announced on Tuesday or Wednesday and must be purchased online. Most are only valid for travel that weekend, but some can be booked weeks or months in advance. Sign up for weekly e-mail alerts at airline Web sites or check mega-sites, such as Smarter Living (www.smarterliving.com), that compile comprehensive lists of last-minute specials. For last-minute trips, www.site59.com in the U.S. and www.lastminute.com in Europe often have better deals than the major-label sites.

If you’re willing to give up some control over your flight details, use an opaque fare service like Priceline (www.priceline.com) or Hotwire (www.hotwire.com). Both offer rock-bottom prices in exchange for travel on a “mystery airline” at a mysterious time of day, often with a mysterious change of planes en route. The mystery airlines are all major, well-known carriers — and the possibility of being sent from Philadelphia to Chicago via Tampa is remote. But your chances of getting a 6 a.m. or 11 p.m. flight are pretty high. Hotwire tells you flight prices before you buy; Priceline usually has better deals than Hotwire, but you have to play their “name our price” game. Note: In 2004, Priceline added non-opaque service to its roster. You can still bid on opaque fares, but you now also have the option to pick exact flights, times, and airlines from a list of offers — most of which are comparable to the prices you’ll find on sites like Expedia and Travelocity.