To book now, or to wait, is a common question forward-thinking travelers ask. If it’s summer Business Class travel to Europe that’s on your mind, the answer is easy.

Now.

Obvious reasons include limited availability of mileage upgrade awards. But the summer Olympic Games in Athens won’t help either. And the best published Business Class fares, which require a 50-day advance purchase, are already filling up for June travel.

When to Use Mileage Upgrades

If you’re looking at airlines like American, Northwest, United and US Airways, you should first consider using miles to upgrade. Reason: These carriers’ lowest economy fares are eligible for upgrade redemption (while others, like Delta and Continental, require paying higher fares for the ‘privilege’ of upgrading).

Best deal: US Airways offers 20,000-mile upgrades valid with “B” fares — as low as $956 for June travel from Philadelphia to Paris (fares are even lower off-season). Remember, US Air miles can be acquired quickly through its partnership with Amex Membership Rewards.

When not to use miles: If Continental or Delta is your carrier of choice, you might be better off saving your miles for a different occasion. Why? Considering Delta’s Atlanta-London upgradeable economy fare of $1,586, and requirement of 50,000 miles to upgrade, why not buy the published Business Class fare outright for $1,900?

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Downside to booking heavily discounted Biz Class fares: Bookings must be made 50 days in advance.

Upside: The additional $314 will save you the 50,000 miles; you'll have an easier time finding available seats on the $1,900 fare (though these fares are not available in all markets); you’ll earn 50% more miles than coach; and 33% more elite credit.

Easy decision.

Best Business Class Values

A few years ago, Northwest introduced a new era of discounted trans-Atlantic Business Class fares, discounted up to 70% off typical full-fares. Priced in the $1,800 to $2,200 range, fares became available between many US cities and destinations all over Europe (assisted by partner KLM Royal Dutch Airlines). Northwest slapped a few restrictions on the fares, like a 30-day advance purchase (now 50 days), and seven-day minimum stay — to keep it out of the hands of their bread and butter business travel customers, mostly unable to travel with these types of restrictions.

Now, as many as eight airlines intermittently offer these fares on routes all over Europe (though often unpredictably), including: Alitalia, American, Air France, Continental, Delta, Iberia, Northwest/KLM, SWISS, and US Airways.

British Airways, offering a lie-flat 180-degree reclining Biz Class seat, initiated a new fare structure of its own in Nov. 2003. Non-stop fares to London — in the $2,699 to $3,200 neighborhood (depending on the gateway and season) — are designed to up-sell leisure travelers willing to meet the airline close to halfway, but are unwilling to spring for full-fare. Again, the fare includes restrictions in an attempt at keeping the heavily discounted fare out of the hands of otherwise full-fare business flyers traveling on company dollars.

Matching British Airways fares to London and Manchester: Lufthansa, United, and Virgin.

Airlines with best discounted Biz Class availability to Europe: Air France, British Airways, SWISS, United, and Virgin.

Limited availability: American, Delta, and Northwest.

More Low-Fare Sleepers Than Ever!

Air France: New, 180-degree reclining Business Class seats can be found on Newark-Paris flights (published Biz Class starting at $2,070); further roll-out of new seats is scheduled over the next 18 months.

Lufthansa: Canadians are the big winners here. Vancouver- and Toronto-Frankfurt flights now offer new Business Class beds; Los Angeles-Munich in April.

KLM Royal Dutch Airlines: On B777-200ERs between New York and Toronto to Amsterdam, you'll find new sleeper seats reclining 170 degrees.

Northwest: Current routes operating new A330s with new 176-degree reclining seats include Detroit-Frankfurt, Detroit-Amsterdam, Detroit-Rome (May 13 - Oct. 29, 2004).

SWISS: Los Angeles-Zurich flights are the first to get delivery of new A340 aircraft, with new lie-flat Biz Class seats. Over a dozen fares from Los Angeles to Europe under $2,400.

Virgin Atlantic: Newly introduced Upper Class ‘Suites’ are installed on New York (JFK)-London flights VS3/VS4 and San Francisco-London VS21/22. Airline sources also say Los Angeles and Newark flights should operate with the new 180-degree reclining seats in March; Miami in April.

Time for bed.