Last week I was staying up late and getting up early to review the latest versions of on-again, off-again fare skirmishes both in Europe and between Anchorage, Hawaii and the West Coast.

Just to be clear: Airlines don’t run ads or issue news releases announcing that fares are going down or popping right back up. But if you happen to be planning a trip in the midst of a fare war, you could score a really good deal. Last Tuesday and Wednesday, some travelers scored tickets to Hawaii on Delta for $128 each way. Anchorage-Portland tickets were available for $108 one-way, before popping back up on Thursday.

At the same time, a big discount wave washed over Europe. Delta and United were the major players, with basic economy fares as low as $456 round-trip between Anchorage or Fairbanks and Barcelona.

Those fares to Europe all have popped back up to the $600 range for round-trip tickets. That’s not a bad price for fall or winter travel to Europe, but I’m quite confident the rates will drop again.

All of the great rates I found were basic economy fares. Travelers buying the cheapest fares board last, which means there’s no overhead bin space. They receive less credit toward their frequent flyer plan and cannot choose their seats in advance. The budget travelers are also last in line for any upgrades, too.

So, the challenge for mileage hounds and upgrade-seekers is how much extra airlines will charge for those add-ons: advance seat assignments, full mileage credit and a decent shot at an upgrade.

[US proposal would bar airline fees for parents to sit beside kids on flights]

When the basic economy fares first were introduced, the upcharge was about $30 each way for most destinations. Between Anchorage and Seattle, Delta still charges $30 more for the main cabin fares, while Alaska Airlines charges $35 each way.

For Saver travelers, Alaska Air awards 30% of the actual miles flown toward a traveler’s Mileage Plan account. Delta doesn’t allow any SkyMiles credit for basic economy flyers.

South of Seattle, the spread between the basic and main cabin increases. Between Anchorage and Honolulu, Alaska Air charges $55 one-way for an upcharge to a main cabin fare on its nonstop flight. Delta charges $50.

Travelers headed to Chicago can fly nonstop from Anchorage on Alaska or United. American also flies each day — but their flights are more expensive. I don’t know why. Both Alaska and United charge $40 each way for an upcharge to the main cabin.

United’s basic economy is particularly onerous regarding carry-on luggage. Unless you pay the upcharge, you’re not allowed to bring aboard a standard-size rolling suitcase to stuff in the overhead bin. If you get to the gate and the agent busts you for trying to smuggle on your suitcase, there’s an extra $25 penalty in addition to the bag fee.

Between Anchorage and Washington, D.C., Alaska Airlines charges between $50 and $84 each way for the upcharge to main. United charges between $50 and $74 each way. Delta charges between $30 and $65 each way.

If you’re traveling within Alaska on Alaska Airlines, all the economy seats are main cabin seats. Further, travelers can check up to three bags at no additional cost.

Both Alaska Airlines and Delta Air passengers can check two bags at no additional charge when traveling to or from Alaska and the Lower 48 or Hawaii. Delta travelers who reside in Alaska must belong to the airline’s SkyMiles loyalty plan. Alaska Air travelers must belong to its Club 49 plan for residents.

Travelers to Europe face a different equation when it comes to the difference between basic economy and the main cabin. The upcharge to main cabin also includes a checked bag.

If you’re flying to Paris, the cheapest fare on Delta in mid-October is $591 round-trip. A checked bag will cost you an additional $150. If you choose to pay $210 more, you can pick your seat in advance and get your first checked bag at no additional cost.

United offers the same package, for a little less: $200. American also charges $200 more and includes a pre-assigned seat and one checked bag (up to 23 kilograms).

Travelers to Asia have a few more twists in the equation. Flying to Singapore, United Airlines has a great fare of $798 round-trip. There’s just one stop in San Francisco on the outbound date I checked (Aug. 29). Even a basic economy ticket includes one checked bag. An upcharge to the main cabin for $160 round-trip includes the fee for a second checked bag.

By the way, United’s return flight from Singapore goes through San Francisco and Denver. It makes for a 30-hour travel day.

Traveling from Anchorage to Tokyo on Delta, the cost for basic economy is $1,552 round-trip. That price includes a free checked bag. The upcharge to main is $260. Once you’ve got your credit card out, though, Delta is likely to tempt you with an upgrade to Comfort+ for an additional $360. That’s a total of $2,172, or $620 more than the basic economy rate. The biggest benefit with Comfort+ is a few inches of extra legroom.

Depending on the airline, travelers to Asia may be able to choose a seat in advance and pay for it even if they’re traveling on a basic economy ticket.

[With seat sizes and passenger priorities changing, the cheapest ticket isn’t always the best]

There are different terms and conditions for traveling to different continents, including South America and Africa. The take-home message is this: The advertised price probably is not what you’re going to pay when you check out. In addition to basic vs. main, there may be additional fees for preferred seating, for any food you pre-order or if you want to pay for priority boarding or to go to a lounge before your flight.

For travelers who compare airlines before making a decision, these additional fees and options make the job harder. A travel agent can advise you on the best options for a flight, including whether or not you’re likely to make a tight connection in … say … Seattle. But the agent will charge an additional fee. Even so, if booking travel is not your core competence, an agent’s counsel could save you a lot of money and aggravation.

It can be confusing to keep track of what airline offers this or that. But it’s worth it to be aware that the optional fees will boost the cost of your next trip.