I think it is written with blood from a scratch. I spoke to a pilot about it a while back, he said in the early days (either because of less EM shielding or dif

I think it is written with blood from a scratch. I spoke to a pilot about it a while back, he said in the early days (either because of less EM shielding or different phone design or something else - not sure) this really interfered with e.g. the landing radio aids. While it never caused a crash, it was mighty annoying and distracting, and in the wrong circumstances could have lead to a crash. AFAIK it never did, but could have done.