The Knee Defender, a gadget that blocks plane seats from reclining, got a global boost after a scuffle between two passengers forced a United Airlines jet to make an unscheduled landing.
The gizmo's website crashed Tuesday after traffic surged, and sales rose "substantially" for the $US21.95 ($A23.57) plastic clips that have been on the market since 2003, said the inventor, Ira Goldman.
While a product that interferes with another flier's comfort may rub some people the wrong way, the issue is airlines' legroom cutbacks, Goldman said. Carriers are shrinking space between rows - Spirit Airlines' allotment is about 10 per cent less than the industry standard - and using thinner cushions to squeeze more people into coach cabins.
"They don't have Plan B for the fact that a lot of people, when they sit down in their seat at the gate, their knees already are hitting the seat-back in front of them," Goldman said in a telephone interview from Washington.
The Knee Defender hit the headlines because of an in-flight squabble on United Flight 1462, which had to touch down on August 24 in Chicago en route to Denver from Newark, New Jersey. One person installed a device that prevented the passenger in front of him from reclining, said Charlie Hobart, a spokesman for United Continental Holdings.
The Associated Press, citing an anonymous law enforcement source, gave a more-graphic account: Upset that her seat was locked, one traveller threw water at a man who employed a Knee Defender and refused to remove it at the request of a flight attendant.
Both people were in United's Economy Plus section, an area in the coach cabin that gives people as much as five more inches of legroom for a fee or elite frequent-flier status at the Chicago-based airline.
Goldman's gadget is a pair of U-shaped clips that fits over the arms of the seat-back tray table, blocking the passenger in front from leaning back. The Federal Aviation Administration prohibits the use of such devices during taxiing, takeoffs and landings, when tray tables must be stowed. The agency said today in a statement that airlines can decide whether they want to allow such devices while cruising.
The four largest US carriers - American Airlines, United, Delta Air Lines and Southwest Airlines - all bar the use of the Knee Defender, spokesmen said. JetBlue Airways, the fifth-biggest, discourages the use of the devices while not specifically barring them.
In Australia, Virgin Australia and Qantas said they also would not allow the use of these devices.
"The use of knee defenders or similar device would be in breach of our conditions of carriage. The safety and comfort of our guests remains our highest priority," a statement from Virgin said. The most pertinent of those conditions is the ban on behaving "... in a manner which would be considered by a reasonable person to be offensive, or in a manner which might cause discomfort, distress, offence or injury to another person," among others.
Qantas said it "would not permit attachments such as the Knee Defender to aircraft seats, and in any event such attachments would need to undergo stringent reviews to ensure they comply with Australian safety regulations in the first instance before being considered."
Australia's Civil Aviation Safety Authority hasn't banned them, but a spokesman said "anything that impacts the safe operation of the aircraft you definitely cannot and should not do ... it appears on the surface that the Knee Defender may not, so it's not a matter for CASA. But we certainly encourage people to not do anything without talking to the airline."
The US industry's standard is about 30 to 31 inches of space between rows. While Spirit passengers have to make do with only 28 inches, some of their seats aren't susceptible to the Knee Defender. They don't recline.
Goldman said he doesn't know which airlines allow them and which don't. He likened his invention to a radar detector, which may be legal and tolerated in many states, if frowned upon.
A 1.9-metre entrepreneur and non-practicing attorney, Goldman said he got the idea for the Knee Defender around 1998 while flying. He took out an umbrella and laid it across the arms of his tray table, noticing that it blocked the seat ahead of him from tilting back. He dusted off the idea a couple years later at the urging of friends.
Soon, he said, he was asking acquaintances to test his invention in flight. One put down her tray table, took out 10 prototypes of his Knee Defender and started experimenting on the seat-back of the person in front of her.
Another day, Goldman was going through an airport checkpoint and was asked to empty his carry-on luggage for a random screening. A Transportation Security Administration employee looked quizzically at him.
"'What is this?'" Goldman recounted the TSA worker as asking. "I explained it, and he smiled and sent me on my way."
Goldman said he sources the Knee Defender from a manufacturer in China. His only advertising expense was $A1.34 to test some Google ads. The product's controversial nature generates its own publicity, said Goldman, who wouldn't disclose annual sales or personal details such as his age.
"But it keeps the lights on," he said. "We sell these things."
During the interview, Goldman returned often to his theme that airlines' legroom cutbacks are the problem, not his gadget or the people who use it. In his view, he is just calling attention to industry practices.
"I was the kid who says, 'The emperor's not wearing any clothes,' " Goldman said. " 'He's naked.' "
Bloomberg with Julietta Jameson