It was a sunny & part cloudy morning,probably the first decent warm day of spring.I was sitting in my garden chatting to my daughter on my mobile phone.I had my camera with me as i was trying to photograph garden birds it is a hobby of mine.Whilst talking i noticed this really weird noise starting up it was a low pitched him & a kind of deep rumbling noise & it seemed to fill the air completely,this was not any kind of aeroplane noise that i have ever heard before.I am very keen on all aircraft & have spent a lot of my life observing them at airshows etc.My dad was in the raf & most of his family worked in the aircraft industry,also have family in the us involved with aircraft design etc.I feel i know a fair bit about aircraft,anyway soon these 6 weird looking aircraft came into view & i mean weird.They had wings of a sort but not the usual type at all,they were kind of made of lots of curves along each wing also they had two sets of wings one behind the other along the body & a strange curved tail.They were shiny reflective metallic & a bright reddy/orangy colour with a silvery cloud like design on each wing that i could see.The speed they were travelling at was incredible,i attempted to get a video of them but they were so fast that nothing came out.It is possible that they are some experimental craft that i know nothing about but i would be surprised if they are.I go to a lot of air displays & i have never seen anything like that flying before or making the same weird noise that these craft made.I was very baffled by it to be honest.I asked around if anyone else had seen them but no-one said they had.A couple of weeks later there was one mention on social media a lady said that she saw & heard some very strange looking & sounding aeroplanes??Said she assumed they were practising for an air display but that they did not look like aeroplanes to her & she found them worrying.So did i to be honest! it might sound odd but i almost felt like they were running on steam or something as they appeared to have something like water vapour around & behind them & the noise somehow reminded me a bit of a kettle.I tried to talk to my daughter on my mobile but it had gone dead,a while after the planes/craft had dissapeared out of sight it started to work again i phoned her & asked if she had happened to see them(she lives 3 miles down the road from me),but she said no she had not.I only wish that i had managed to get photographic evidence of what i saw.This incident left me a bit shaken up because i could not work out what i had seen & heard.I should have perhaps reported this before now but i could not make up my mind what i had seen & did not want to waste your time.I was talking to someone the other day & mentioned what i saw & they said that i should have reported it...So i have now.The closest description i can come up with is a bit like a rocket but with wings 2 sets one behind the other & a strange tail plus a kind of nose cone.Very shiny metallic & kind of reflective.I have no idea what they were or what they were running on judging by the strange noise that filled they air before & during the time i could see them.I rushed through the house & out through the front door to see if i could see them after they went out of my sight but could not see anything in the sky by then other than another ordinary small aircraft.I can supply a sketch of what i saw if you want or need it.