Frequent Flier Bonuses Launched : Free miles and round-trip tickets to Europe are among new program incentives.

Usually it’s your friends who get the best deals. You know, “companions fly free,” etc. But here’s a chance for their travel to benefit you.

Continental Airlines is having an enrollment drive, and members of its OnePass frequent-flier program can get hefty bonuses when they sign up their friends (or relatives, co-workers--even total strangers).

The only catch is that you also have to persuade these new members to do a lot of traveling during the next few months. The more they do, the more you benefit. You can sign up as many new members as you like, so you might want to go after substantial itinerant groups--say, the New York Mets.

For each new convert who travels a minimum of 5,000 miles by June 30, you can earn points equal to the mileage the new member flies, up to 9,999 miles; you’re credited with 150% of the mileage your friend flies between 10,000 and 14,999, and 200% of the miles over 15,000. Each person must be enrolled on a special form, which you can order by calling the airline. If you’re not already a OnePass member, you can join at the same time. You won’t be eligible for the above perks for recruiting yourself, but you’ll get 2,500 bonus miles after you’ve taken your first flight as a new member.

The February issue of Best Fares, where I learned about this promotion, was a gold mine of other tidbits as well. Best Fares offered a tip that might help OnePass members entice new enrollees: Buy any of Entertainment Publications’ numerous 1992 books of dining and lodging discounts for various cities, which also contain two virtually unrestricted coupons each worth $100 off Continental flights (the books range from $30 to $40; for information, call 800-477-3234).

Two other airlines have announced new frequent-flier bonuses that are likely to set off a flurry of one-upmanship. United is offering a free round-trip ticket to Europe to Mileage Plus members who fly United round trip to the Continent before June 15 (you have to let United know before you go). Then your next flight is on the house. You have a choice of a free round-trip ticket to Europe or one of 10 countries in Latin America (you can go between April 15 and June 15 or from Sept. 15 to Dec. 17). To register--or join Mileage Plus--call (800) 841-4655.

British Airways is offering something similar through its new Executive Club Frequent Traveller Programme USA. Despite its name, to join you don’t even need to have a job, never mind a corner office.

You get 10,000 free bonus miles after the first paid British Airways transatlantic flight by the end of the year. Since a New York-London round trip logs 6,916 miles, one trip plus the 10,000-mile bonus immediately qualifies you for a free round trip between London and any of dozens of European cities.

No blackout dates will be imposed on awards taken on BA transatlantic flights, up to four household members can pool awards, and you can redeem BA miles for flights on American Airlines in North and South America after April 1. For information, call British Airways at (800) 955-2748.