Despite America’s supposed increase in airport security, departure is still proved only by the airline remembering to collect the slip from your visa or visa-waiver form. If it isn’t collected or processed properly, you’re in trouble, as you stand a fair chance of being treated as an overstayer. When you next enter the USA, you will be taken for “secondary processing” at a charming facility where you will be treated as a potential “illegal” until you can prove they are wrong and you are right. Surely a small fraction of that Homeland Security budget could be used to record departures properly? Keith Atkinson, London

Other readers respond.......

I read this with sympathy. An airline failed to return the slip from my visa form some years back and, despite frequent trips there, I am always pulled over for “secondary processing”. One official told me this would happen for the rest of my life. I could understand being pulled over once, but all this fuss for an obvious “paperwork” error is surely a waste of manpower. Tony Goddard, Kent

Help is at hand. We noticed at Atlanta airport last week that machines now “record your departure”. You swipe your passport, provide left and right digital fingerprints, then have your picture taken by a webcam. A little slip is produced for you to cherish and use as evidence when you next enter the USA. Peter Reed, York

It seems that Mr Atkinson's complaint has been addressed stunningly quickly. I have just returned from Atlanta, US. A new procedure requires you to stand at a booth, swipe your passport, have your index fingers scanned and photo taken. A printed receipt must then be handed in to allow you to board your aircraft. One assumes the information is compared with the same provided on entry, and there is an accurate record of departure. Paul Turner, Glastonbury, Somerset

US-Visit says: “The exit procedures being trialled at Atlanta are part of the enhanced biometric security measures. They will be added to visitors’ records to document their status for future visits.”