And airlines are not the only ones betting on the concept.

Planely, a Danish start-up, allows registered users who submit their itineraries to view the Facebook and LinkedIn profiles of others who will be on flights with them. Since it began in late 2010, Planely has connected more than 1,500 travelers, according to its chief executive, Nick Martin.

Satisfly, based in Hong Kong, allows users to submit profile information as well as their flight “moods” — whether they would prefer to talk shop or chat casually — and other details like languages spoken and preferences about potential seatmates. The information is then shared with its airline partners, which incorporate the data into their own seat-assignment platforms.

KLM’s service is available only to travelers with confirmed reservations who are willing to connect their social profiles to their booking. After selecting the amount of personal information they wish to share, passengers are presented with seat maps that show where others who have also shared their profiles are seated. You can then reserve the seat next to anyone who seems interesting — provided it is available — and that person will receive a message with your profile details.

On a flight from Amsterdam to São Paulo this week, for example, you could have chosen the director of a British answering service, who has a passion for reggae and jazz; an Italian chemical engineer fluent in Dutch, English, Spanish and Portuguese; or a Norwegian alternative-rock fan en route to visit family in Argentina.

While it is not possible to “reject” a person who has chosen to sit with you, you can select another seat as long as two days before the flight. Those feeling awkward about moving can delete their data and select new seats using the standard — anonymous — online platform.

Dan Nainan, a comedian from New York, said he was eager to try it out.

“If people are able to choose whom they sit next to, they’re more than likely going to be friendly and outgoing and easy to talk to,” said Mr. Nainan, 30, who said he had no reservations about making his personal data available to fellow passengers. “I’ve met some wonderful people on airplanes and made some great connections. I would love to be able to see the selection of people that I could potentially sit next to.”