Originally Posted by Shareholder

Rather oversimplification. FCC regs are generally the ones followed by most countries vis a vis aircraft safety compliance. And while we have known for years that such devices have little or no effect on modern navigation and other aircraft systems, the regulations of the US and most other countries require tests to prove this is the case on each type of aircraft involved, which would also include generational variations of the same aircraft type. The FCC recognized that it would take each airline many months to do such evaluations themselves and accepted the singular testing by aircraft type manufacturers to fast track the rule change and thus take applications by airlines to permit the use of these devices.

BTW there are still a number of major US regional carriers that have not received FCC permission six months after the go-ahead. Whether this is due to the FCC's delaying the process or the airlines not bothering to apply is open to debate.