Most of the Bay Area’s biggest carriers are piling on the miles for frequent flyers this fall, making it easier than ever to attain or maintain elite status for next year. American gets the credit for kicking off this latest mileage bonus trend, followed by United. Then today, Southwest joined the party. Here are the various deals:

>Southwest: Rapid Rewards members who book and travel between Sept 17 and Oct 31 get one bonus Rapid Rewards credit per one-way flight in addition to normal earnings. This means you’ll earn four credits for every round trip, so if you make four round trips during the promotional period, you’ll earn 16 credits, enough for a free flight. Business Select customers will REALLY like this offer because they’ll earn 4.5 credits per round trip for flights less than 750 miles and six round trip credits for longer flights. Registration is required: www.southwest.com/rrbonus

>American AAdvantage members get double elite qualifying miles now through Dec 15. Register at www.aa.com/elite

>United Mileage Plus is offering double miles OR double segments, but not both through Dec 15. Register for double miles here: at www.united.com/offer/mpw049. If you typically fly more short-stage flights, go for the segments. Register here: www.united.com/offer/mpw059.

Also on the mileage front…..

Elite bonuses: United is making a special offer to Elite members who will earn at least 35,000 miles by the end of the year. They’ll get to choose between a one-time Red Carpet Club pass ($50 value) and 7,500 bonus miles. If you are Premier Exec and earn at least 75,000 by the end of the year, you get two Red Carpet passes ($100 value) or 15,000 miles. 1K Members who earn at least 125k miles get two systemwide upgrades or 25,000 miles. (You must sign on to your Mileage Plus account to register.)

American’s making a similar offer to it’s elite flyers: Gold members who fly between 40,000 and 50,000 miles by year’s end will be able to choose between two 500-mile upgrades, a one day Admirals Club pass or 7,500 bonus miles. Platinums who fly 75,000 to 100,000 miles choose four 500-mile upgrades or two Admirals Club one-day passes, or 15,000 bonus miles or one-year Gold status for a friend. Executive Plat members who fly 125,000 EQMs by year’s end can choose two one-way systemwide upgrades, a one-year Admirals Club membership, 25,000 bonus miles or the ability to gift a friend AAdvantage Gold status for a year.