Our Next Question comes from our boss, 9NEWS general manager Steve Carter: why do airlines still include the international symbol for "no smoking" on new airplanes?

Former NTSB investigator Greg Feith tells us that while smoking's been banned on flights since 1988, many planes still in service were built before then. Changing anything on an airplane involves a lot of red tape, so some carriers may have left the no smoking signs to avoid hassle.

Some passengers clearly need the reminder, too. Since 2000, nearly 700 people have been prosecuted for smoking on an airplane.

Feith told us some newer generation planes have replaced the no smoking sign with one that says "please turn off electronic devices."

So there ya have it, boss.

That's the reason why there are "no smoking" signs are still on planes.

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