but how long until an airline gets sued because a passenger was unable to take an emergency-related call?
If you leave it to the market and then a passenger chooses to buy a ticket on a no-phones airline, then it's the call receiver who is responsible for declining the emergency call. "Our customer wanted to be in a phoneless environment and paid for that, furthermore demonstrating his preference. Sue him for not taking your call."
Furthermore, it's hard to imagine any scenario where anyone could ever have a reasonable expectation for being able to take an emergency call. Even if I fab an extreme over-the-top example (as I, like anyone, would love to do).
Guy happens to be the Last Doctor In The World. He says, "I want to fly on someone else's airplane, but I want to not listen to anyone else talking." So he buys a ticket on a no-phones airline. While waiting in the terminal, he turns off his phone. One second later, the President's wife calls him, and leaves this voice mail: "The President is choking on pizza! What do I do? WHAT DO I DO!?" but since the doctor turned off his phone, he doesn't see the call come in. He boards his flight, oblivious to the coming disaster.
Mid-flight, one of the passengers starts talking to another passenger. The doctor screams, "hey, shut the fuck up!" and everyone quiets down, because you never know when you might want to be on The Last Doctor In The World's good side. The captain makes an announcement over the intercom. The doctor glares, hatefully. He doesn't make a scene, but he writes the captain's name in his no-treatment book. The engines drone on, and he grimaces with discomfort, noting he's never going to treat anyone who works at Boeing, where they make such loud engines.
An hour later, he gets off the plane. He turns on his phone, and sees a bunch of voicemails from the First Lady. He calls her back. "Get your husband to cough up the pizza," he offers, rolling his eyes, but his advice has arrived too late. The president has already asphyxiated to death.
Unfortunately, right after the president's death, a bill arrived on his desk, which would have outlawed mass puppy shredding. It didn't get signed quickly, because it took a while for the then-vice-president to catch up. So one hundred thousand puppies where shredded, while it was still legal to do so. One of those puppies had an important passphrase tattooed on its ear, but now it has been shredded. Without the passphrase, no one was able to stop the nuclear launch that resulted in the deaths of three billion people.
One of the people whose gardener died in the nuclear war, sues Samsung for designing a phone that has an off switch, based on the idea that people HAVE TO receive emergency calls, no matter what anyone (even the owner of the phone) wants.
You're on the jury. What's your decision? If you rule in favor of the plaintiff, Samsung owes someone $3 to replace the plant that the dead gardener never got around to watering. And I will harbor a hypothetical-$3 grudge against you, from now to the end of time. OTOH, if you rule for the defendent, then I agree with you, my friend. What's it going to be?