Police secretly investigated the travel habits, family, friends and backgrounds of 47,000 innocent people last year after they bought plane tickets to fly into and out of Britain.
The intrusiveness has provoked fury among civil liberties campaigners and now may be stopped by Britain's new coalition Government.
The flyers were singled out by the 'terrorist detector' database, introduced by Labour, monitoring millions of British tourists and other travellers.
Checks included scrutiny of the police national computer, financial records and analysis of 'known associates' before people were cleared for travel.
Yet it is understood the £1.2 billion system has never led to the arrest of a terrorist - and police now use it to target 'sex offenders and football hooligans'.
Police have also used it to produce 14,000 intelligence reports on travellers for 'future use'. They can be shared by security services worldwide.
'Suspect' requests likely to lead to innocent holidaymakers receiving 'red flags' as potential terrorists include ordering a vegetarian meal, asking for an over-wing seat and travelling with a foreign-born husband or wife.