Unions warned today that new EU rules could threaten plane safety.
Pilots' union Balpa and cabin crew union Unite have sent Downing Street a sackful of scientific evidence showing that the new rules on pilot fatigue are not safe.
Copies of the reports, correspondence and testimonials also went to the Department for Transport and the Civil Aviation Authority, who are due to decide on whether to yield to Europe's lower safety limits.
The European Aviation Safety Agency wants to replace Britain's current rules with ones that could see pilots trying to land planes after being awake for 22 hours or more.
It also plans to slash the number of pilots required on very long flights and scrap restrictions on early starts and overnight work.
Balpa general secretary Jim McAuslan said: "We have done everything we can to warn ministers, politicians, civil servants and EU bureaucrats about why these rules are unsafe and could endanger passengers. Now, frankly, it's over to them.
"Pilots and cabin crew are united on this. Fatigue regulations must be safe, they must be scientifically sound and they must recognise the danger that fatigue presents to the travelling public."
Unite national officer Oliver Richardson said: "The proposals are hugely worrying for cabin crew and airline staff. We are working closely with our pilot colleagues to ensure decision makers are aware."
Crew and pilots also took part in co-ordinated national activities and actions today to highlight the safety risk.