Tell anyone under the age 18 or so that you used to be able to smoke on planes and their reaction is likely to be utter disbelief.
"You aren't even allow to smoke in some parks these days, so why did they once let you spark up in an air-tight, flying carriage?" they might wonder.
And they'd be right. It seems crazy that passengers could once buy cigarettes from the cabin crew then light them at 30,000 feet without a care in the world. Second-hand smoke? '
However, no matter how ridiculous in-flight smoking may seem today (all planes were smoke-free by the end of end of the 90s), there remains on aircraft around the world a constant – and mandatory – reminder of those hazy days: the ashtray. Why?
According to the Federal Aviation Administration's (FAA) list of "minimum equipment" for aircraft, an ashtray in the plane toilet is a legal requirement.
Yep, despite smoking on a plane being long-gone, bar a few belligerent celebrities, the FAA rules that lavatory doors must still be fitted with ashtrays because if someone were to have, illegally, a cheeky fag, they still need to stub it out, and it's best they have somewhere to do that rather than cause a fire by dropping it in the bin.
What's more, if one of the aircraft's ashtrays breaks, regulations say they must be fixed or replaced within 10 days (as long as 50 per cent of the plane's ashtrays are operational, otherwise they must be fixed in three days).
Indeed, in 2009, it was reported that a British Airways plane was delayed as staff were searching for a "vital" ashtray.
A spokesperson at the time said: "It is a legal requirement, under air navigation orders, to have ashtrays because while smoking is not permitted on flights, if someone were to light a cigarette on board there must be somewhere to safely extinguish it."
To perfectly illustrate the dangers, in 1973, 123 passengers died on Varig Flight 820 from Rio de Janeiro to Paris after a fire broke out when a cigarette was thrown in the rubbish bin of the toilet. The cabin filled with smoke and the pilot was forced to make a crash landing in a field about 15km south of the French capital.
That said, the Civil Aviation Authority (CAA), the FAA's British sibling, says there is no mention of mandatory ashtrays, only that smoking is illegal on planes.
A special mention must go to always-defunct airline, SmintAir (short for Smoker's International Airlines), which tried in 2004 (after it had long been illegal) to launch a carrier aimed at businessmen who still wanted to smoke in the sky. It wanted to fly two Boeing 747s between Dusseldorf and Tokyo but its financing fell through at the last minute when the bank pulled out.
Despite the FAA regulations, the presence of ashtrays even seems to bewilder the senior management of some airlines.
In an 2008 article, writer Sam Leith discovered the silver-grey quirk on the inaugural flight of a new Airbus A380, along with "always-illuminated, no-smoking signs".
"When I asked a spokesman for Singapore Airlines, he confessed that even the company's CEO had been baffled as to what they were doing there," he said.
The Telegraph, London