If this can help Bobby, every passenger plane has a secondary back up system, for the miles they travel in comparison to a car, they are the safest form of travel, Jumbos ( 747) can land on one engine ( They have 4, your journey to any UK airport is, & can be harrowing regards risk of a collision & death, its not often you see headlines regards car crashes & there are Hundreds every day with deaths, granted when a plane goes down the papers are full of it, Google the flight deck & show you MIL the view that the pilot & Co pilot have & the safety procedure that is done before the flight even begins. Pilots are one of their in as regards Training & don't forget, he / she wants to get home to, people have problems regards flying as they do not know what is happening within a tube ( the fuselage) the area where you sit. If you go to the Viewing area at Man Airport there is an old Comet there for you to view, it costs a fiver for the day & well worth the visit, this may help her. Good Luck, & I hope your MIL overcomes her fear, we have travelled thousand's of miles & like other people on this site, we are still here.