I will be upfront and state this is a plug for something so apologies if this is not permitted/frowned upon, but... ... I guess most of us fly once or twice a year (probably more) and take for granted the ability of the planes to land and take-off regardless of the weather or visibility. All of this is only possible thanks to radar research carried out during World War II using an elderly airliner, Boeing 247D DZ203 which was shipped over to the UK especially for use in radar trials. My Dad has spent the last few years researching the work carried out at RAF Defford (amongst other places) using the Boeing and has self-published a book covering the whole subject. Feel free to have a look at Amazon (Top Secret Boeing: Amazon.co.uk: Bob Shaw: Books) or eBay to get it directly from him. Thanks for reading and I hope one or two may be interested in investigating further.