Believing there was a bomb on board she informed the captain and constantly looked at her watch in panic.
The captain asked Davis to write a report of the incident and noticed that it was in the same handwriting as the message.
Davis was relieved of his duties for the remainder of that flight and when they touched down in Tokyo he was put on another aircraft as a passenger and sent back to London.
He was arrested at Heathrow on February 11 where he admitted the offence.
Sam Bonner, defending, told the court that her client never meant to cause any great panic on board the flight as he had not intended for any passengers to see the note.
'He was due to make checks of the aircraft and he himself wrote this on the door just as he was doing the checks.'
She explained that Davis had been having a tough time financially and hoped that by demonstrating a cool head in a crisis and 'saving the day' he would be given a promotion at work.
'His only intention was for staff to see it and for his own gain at work,' Ms Bonner added.
Judge Anna Guggenheim QC said: 'You wanted to cause a crisis in order to be seen to equip yourself well, to be seen well by your employers to rise in the estimation of your employers.
'To put it simply, to be a hero.'
She added that his behaviour had been 'extremely dangerous' and had it not been for the 'good judgement' of the captain the flight would have had to diverted for an emergency landing causing all those on board to be terrified.
Davis, of,Three Bridges, Crawley, south London, was sentenced to six months imprisonment.
He had admitted communicating false information with intent at an earlier hearing.
Dressed in a black suit, white shirt and black tie, he remained emotionless as he was sentenced.