Twitter users who visited Delta.com over the last few months may have seen promoted tweets from the airline in their Twitter feeds, urging them to book a flight, or if they already had a reservation, to upgrade to an Economy Comfort seat.

The latter promoted tweet about Economy Comfort seats would have appeared up to 48 hours before the flight.

The advertising initiative took place as Delta participated in a Twitter beta of its tailored audiences targeting product. Twitter announced today that the product, which it previewed in July, is now available globally.

Twitter has certified several technology partners, including Adara, which worked with Delta and its advertising agency, Digitas, on the two campaigns, for tailored audiences.  Other approved tech partners include AdRollBlueKaiChangoDataXuDstilleryLotameQuantcastValueClick, and [x+1].

“To get the special offer to those people who are also on Twitter, the hotel brand [or other advertiser] may share with us browser-related information (browser cookie ID) through an ads partner,” Twitter says. “We can then match that information to Twitter accounts in order to show the matched users a Promoted Tweet with the travel deal.

Twitter says it supports Do Not Track and doesn’t receive cookie information from advertisers if the user enables Do Not Track.

“The end result is a highly relevant and useful message for the user,” Twitter states.

While Hubspot stated it saw a 45% increase in engagement rates and Krossover reported a 74% decrease in cost per customer acquisition as part of the Twitter beta for tailored audiences, neither Delta nor Digitas revealed precise statistics for the airline’s campaigns.

“We were pleased with the campaign’s initial performance and excited about the opportunities that the tailored audiences product represents moving into 2014, said Breanne Loso, media planner for Digitas.

In its blog post, Twitter portrayed how the retargeting process might work for a hotel advertiser.

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Adara CEO Layton Han believes the retargeting will be especially helpful for travel advertisers who seek to reach potential customers at critical moments because it has access to real-time information about consumers during the booking process, for example.

Photo Credit: Delta's Economy Comfort seats on an A330 aircraft. Delta used Twitter to target travelers with flight tickets, prodding them to purchase Economy Comfort seats. Delta Air Lines