Friends,
My job deals with Air Traffic Control systems (I'm not a controller... I am an engineer for a company that makes all sorts of ATC electronics systems). You can be assured that neither the FAA nor Eurocontrol (the European version of FAA) will require any navigation or landing system without years of testing. And re-testing. And more testing after that. GPS has been under study for at least 10 years... Galileo will receive the same scrutiny when it is operational. That means that adoption of any GPS +/- Galileo system for precision air navigation or landing is a LONG way off.
Having said this, AMSAT planners should know that any amateur interference or intrusion into the GPS & Galileo "band" would be supremely foolish. All the arguments about how ham radio is great in emergencies will count for nothing the first time an aircraft crashes after losing its satellite navigation due to interference. I have been a ham for 35+ years and love the hobby dearly, but we must keep in mind that in the Big Picture, we are not very important. The FCC and its European counterparts will yank our 13cm ("L" band) allocation in a heartbeat if we interfere with GPS/Galileo.
73, W9IP