It was at the centre of a spat that led to a plane being diverted.
And interest in the gadget is now so great that its company's website crashed on Tuesday.
The Knee Defender, which blocks airplane seats from reclining, got a boost after the incident on Sunday.
Website traffic surged and sales rose "substantially" for the US$21.95 (S$27) plastic clips, reported the Washington Post.
When attached to a tray table, the Knee Defender jams the reclining mechanism of the seat in front.
It made the headlines after United Airlines Flight 1462, en route to Denver from Newark, New Jersey, on Sunday made an unscheduled landing.
Mr Charlie Hobart, spokesman for United Continental Holdings, said a passenger installed a device that prevented the person in front of him from reclining.
The Guardian reported that the man, seated in a middle seat of row 12, used the Knee Defender to stop the woman in front of him from reclining while he was using his laptop.
A flight attendant asked him to remove the device and he refused. The woman then stood up, turned around and threw a cup of water at him, said a law enforcement official, who spoke on condition of anonymity.
Both were in United's Economy Plus section, an area in the coach cabin that offers about 13cm of extra legroom for a fee or elite frequent-flier status.
Transportation Security Administration (TSA) spokesman Ross Feinstein said the dispute escalated to the point that the airline decided to divert to Chicago's O'Hare international airport.
Chicago police and TSA officers spoke to the passengers involved, both 48, and "deemed it a customer service issue", Mr Feinstein said.
The plane continued on to Denver without them. It arrived an hour and 38 minutes late, according to the airline's website.
This article was first published on August 28, 2014.
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