A mail pack, which will be sent to silver and gold members of bmi's diamond club loyalty scheme, contains application forms in the form of postcards, which recipients can either send or hand to friends.
The postcards feature pictures of bmi destinations such as Rome, Paris, Milan and Edinburgh, upon which the strapline "see where being a good friend gets you" is written in mock handwriting.
Every recipient will be rewarded 3,000 destination miles for every friend they recommend. Once four recommended friends have flown with bmi, the recipient will earn a free European trip. The friends will themselves be offered an initial 3,000 destination miles as an incentive to join the diamond club.
The mailing will be supported by point of sale in bmi airport lounges, banners in the diamond club section of the bmi website and e-postards.
The Andrews Aldridge managing partner Phil Andrews explained: "Postcards are a natural way for friends to communicate with each other, so there was a natural fit for an MGM campaign for a club. With the addition of a handwritten strapline, the campaign has a very natural feel to it."
Juliet Hutchins, the bmi diamond club manager, added: "We just want to make sure that all of our customers and potential customers are getting the most out of the club. The campaign means we're rewarding existing customers and getting new ones simultaneously."
The promotion was written by Kristian Foy and art directed by Mark Hanson.