Yesterday afternoon I was working in the garden and spotted something flying alongside a conventional low-wing single prop monoplane. I pointed it out to friends with the words "what the heck is that?" but they're not aviation-minded and wouldn't know the difference between an Airbus and a sorbet. I've tried googling delta-winged private/small aircraft and all things of that ilk, but I can't find anything that even comes close. All I know is it was flying towards IWM Duxford airfield, and both it and the monoplane were together - a wing's length apart - and same speed, about 110-120kts. It looked to me like they were travelling together, ie two buddies going from A to B and were keeping pace. There's no way the monoplane pilot could have missed it, and if it had been a UFO I doubt anyone would want to fly alongside it. Me, I'd be bank right, full throttle, nose down, anything to get away from it. The way the monoplane pilot flew in a straight line with this thing right next to him means he was either blind, or it was man-made. I couldn't tell if the object had a prop, but definitely no vertical tailplane, and looked about 20-25ft long. I'm stumped. Not saying it's a UFO, as the way it kept with the monoplane, and the monoplane seemed to be travelling with it, made me think it was man-made. And anyway, UFOs are meant to be round. I've never seen anything like it. Does anyone know, or have a clue, of any planes that look like this? edit: I've emailed IWM Duxford for advice, as it's the nearest airfield, but not expecting a reply back. What the object would have looked like from above/below: And as I saw it from below and to the side (pointy end travelling forwards, ie down and to the left in this image): And direction of travel compared to me. (A random street view, not mine, used to show direction of travel in relation to me, to show that I could see the underneath, its profile, and also that my view should have enabled me to see any tailplane).