Wondering how you can get a few more miles into your frequent flyer account before it's time for vacation? The answer—according to American Airlines, anyway—is to ship more air cargo.

American Airlines Cargo recently expanded its Business ExtrAA program, which now allows customers to earn frequent-flyer miles for shipments of any size. Shippers will earn 2,000 points—the equivalent of an advance-booking, economy-class flight within the continental United States, Canada, and Mexico—for every $40,000 in eligible shipping revenue. Express freight earns an extra 20 points, while online bookings receive a bonus of 5 points.

Why is American crossing the normally sharp divide between passengers and cargo? It's all about maintaining and rewarding customer loyalty, said David Brooks, president of AA's cargo division, in announcing the expanded program.

There are restrictions and conditions, of course; only the line-haul portions of American's own flights are eligible, for instance. But shippers who manage to meet all the criteria conceivably could earn the maximum of 200,000 points per year.