> Techum, hotzaah, muktza.
They are not doing anything and not benefitting from any of these. All they did was – got back into the plane upon a lawful government order. They do not care whether the plane will stand on tarmac for a day or fly over the whole world. So, there is surely no issur mdeuraita. And concern for the health of other Jews should surely overrride any other concerns they have.