The Toronto Star reports that Aeroplan has taken steps to prevent customers from reselling the airline’s coveted upgrade certificates on the Internet, arguing the abuse would prevent its best customers from using their own certificates.

Aeroplan Income Fund, which generates revenue by selling points to companies that then issue them to consumers for making purchases such as airline tickets, is beginning to personalize newly issued upgrade certificates by printing the customer’s name and Aeroplan number of each certificate. The certificates allow flyers with a lower-class ticket to upgrade to a higher-class seat.

The company is betting the move will help to deter some of its 5 million members from reselling certificates on the Internet, The Star said.

Aeroplan spokesperson Michele Meier told the paper that besides eliminating an after-market for upgrade certificates, which she suggested might be illegal, the move also would help bolster relations with customers.

“Some of our customers get their luggage tags with their own names on them and they’re very proud,” Meier told The Star. “They like having their names on, because it says they’re an important customer of this company.”

With 140,000 elite members, it’s clear that some flyers have more certificates than they’d use. Super Elite members, for instance, can collect more than a dozen upgrade passes each year.

According to the paper, there were 13 listings on eBay’s Web site for Air Canada upgrades. One Toronto-based seller had offered for sale a system-wide upgrade pass with an opening bid price of $20.

Similarly, a pair of special system-wide upgrade certificates, which can be used by Air Canada’s most frequent customers for tickets purchased at lower-cost fares, was being offered by a London-based seller for $8.72.