Cathay Pacific is now offering business class and premium economy upgrades via online auction on selected routes, with bump-ups going to the highest cash bidder.

Dubbed Enhance, the upgrade auction scheme is currently available for economy and premium economy passengers on selected flights between Hong Kong and Perth, London, Paris, New York/Newark, Toronto, Moscow, Seoul, Surabaya and Cebu.

Only passengers on certain flights and booked into specific ticket classes, with travel from June 20 through to November 12 2014, are eligible to bid for a better seat, however – to check if your booking is auction-friendly, enter your booking reference number and family name at cathaypacific.com/enhance.

Bookings made using frequent flyer points are among the ticket classes which aren't eligible for an upgrade, no matter how much money you're willing to bid.

Cathay Pacific says that travellers who are eligible for Enhance will receive an instant invitation on the booking confirmation page if they book online, or will receive an email invitation seven days before departure if they booked through a travel agent.

"Follow the steps on the invitation, submit your personal information, and make an offer." the airline explains. "If your offer was accepted, we will contact you 2-3 days before your flight to confirm the upgrade."

For more details on Enhance, click through to upgrade.cathaypacific.com.

PREVIOUS | Cathay Pacific is considering offering upgrades to premium economy, business and first class via online auctions.

The move would see passengers bidding for upgrades using cash, along similar lines to the upgrade auctions already held by other airlines including Air New Zealand, Virgin Australia, Virgin Atlantic and Etihad.

"Customers would be invited to place an offer for their booked flights via a website prior to their departure date" a spokesperson for Cathay Pacific explains.

"If their offer was successful they would be advised around four days prior to departure and the offer payment collected."

The plan could help Cathay Pacific fill the premium cabins on its flights by making all premium seating available to any passenger.

However, it has understandably stoked fears among members of Cathay Pacific's Marco Polo rewards program that this could reduce the number of upgrade seats available to frequent flyers.

"We are examining new initiatives that will allow us to offer passengers, including our Marco Polo Club members, different ways to get an upgrade" a Cathay Pacific spokeswoman told The South China Morning Post.

"At this stage the project is still in the study phase."

Follow Australian Business Traveller on Twitter: we're @AusBT