Updating the total when any of a set of spinners changes its value
You could use a jQuery object to query all four of the spinners.

function sum(values) {
    return values.reduce(function (prev, next) { return prev + next; }, 0);
}

function inputToInt(input) {
    return parseInt($(input).val());
}

$('.spinner-input, #flight-class').change(function() {
    var passengerCounts = $('.passenger-list .spinner-input');
    var totalCount = sum(passengerCounts.toArray().map(inputToInt));

    var fc = $('#flight-class option:selected').text();

    $('#kisi-sayisi').val(totalCount + ' - ' + fc);
});