The fares you see listed on TripMania are for round-trip travel, unless it's noted otherwise. Almost always, the prices don't include most of the taxes and fees that you're required to pay. On domestic flights, these additional charges can total up to $40, and on international flights, up to $100 or more.

In general, when you see a listed fare, it includes a 7.5 percent federal excise tax, as well as fees levied by the airline, including fuel charges, if there are any. However, it does not include additional government-imposed taxes.

On domestic flights within the continental U.S., you can expect to pay:

• a $3.10 federal segment fee for each takeoff
• $3 to $4.50 in airport charges (known as Passenger Facility Charges or PFCs) for each takeoff, depending on the specific airports you fly from, up to a maximum of $18
• a $2.50 security fee for each takeoff from a U.S. airport, up to a maximum of $10

For typical round-trip domestic flights, the taxes and fees work out to:

Nonstop flights:

• $6.20 in federal segment fees
• $6 to $9 in airport charges
• $5 security fee
  
  Total: $17.20 to $20.20

Connecting flights with one stop:

• $12.40 in federal segment fees
• $12 to $18 in airport charges
• $10 security fee
  
  Total: $34.40 to $40.40

For domestic flights beginning or ending in Alaska or Hawaii, you can also expect to pay a Travel Facilities Tax of up to $13.80 per round-trip.

For international itineraries, foreign and domestic fees can total up to $200, depending on your routing and destination. U.S. government-imposed charges include a $13.70 international departure tax, a $13.70 international arrival tax, and $15.10 in immigration and customs fees. Foreign taxes will fluctuate based on the prevailing exchange rate. As an example, passengers departing from London (Heathrow), England, can expect to pay departure taxes of between 28 and 48 British pounds (approximately $44 to $75). So, for your round-trip ticket to the U.K., your taxes and fees will total between $86 and $117.

Sometimes, you won't be able to book a fare at the price we've listed, even when taxes and fees are taken into account. That could be because seats are sold out at the lowest rate, or because your travel plans don't meet the rules of the specific fare, which may require travel on certain days or a minimum stay.

In addition, charges for optional services can sometimes raise the price you pay. These include a $10 to $25 charge for using paper tickets on certain airlines if e-tickets are available, a service fee, $5 or $6 per ticket, for booking at an online travel agency such as Expedia, Orbitz, or Travelocity, and a minimum $19.95 shipping charge for paper tickets from these same companies.